doc: add a link to the public API on the main page
[libam7xxx.git] / src / am7xxx.c
index 11c259d..1035e23 100644 (file)
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <stdarg.h>
 #include <errno.h>
 #include <libusb.h>
 #include <errno.h>
 #include <libusb.h>
+#include <math.h>
 
 #include "am7xxx.h"
 #include "serialize.h"
 
 #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
 
 
 #include "am7xxx.h"
 #include "serialize.h"
 
 #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
 
+/* If we're not using GNU C, elide __attribute__
+ * taken from: http://unixwiz.net/techtips/gnu-c-attributes.html)
+ */
+#ifndef __GNUC__
+#  define  __attribute__(x)  /*NOTHING*/
+#endif
+
+static void log_message(am7xxx_context *ctx,
+                       int level,
+                       const char *function,
+                       int line,
+                       const char *fmt,
+                       ...) __attribute__ ((format (printf, 5, 6)));
+
+#define fatal(...)        log_message(NULL, AM7XXX_LOG_FATAL,   __func__, __LINE__, __VA_ARGS__)
+#define error(ctx, ...)   log_message(ctx,  AM7XXX_LOG_ERROR,   __func__, __LINE__, __VA_ARGS__)
+#define warning(ctx, ...) log_message(ctx,  AM7XXX_LOG_WARNING, __func__, 0,        __VA_ARGS__)
+#define info(ctx, ...)    log_message(ctx,  AM7XXX_LOG_INFO,    __func__, 0,        __VA_ARGS__)
+#define debug(ctx, ...)   log_message(ctx,  AM7XXX_LOG_DEBUG,   __func__, 0,        __VA_ARGS__)
+#define trace(ctx, ...)   log_message(ctx,  AM7XXX_LOG_TRACE,   NULL,     0,        __VA_ARGS__)
+
 struct am7xxx_usb_device_descriptor {
        const char *name;
        uint16_t vendor_id;
 struct am7xxx_usb_device_descriptor {
        const char *name;
        uint16_t vendor_id;
@@ -47,7 +70,7 @@ static struct am7xxx_usb_device_descriptor supported_devices[] = {
 };
 
 /* The header size on the wire is known to be always 24 bytes, regardless of
 };
 
 /* The header size on the wire is known to be always 24 bytes, regardless of
- * the memory configuration enforced by different architechtures or compilers
+ * the memory configuration enforced by different architectures or compilers
  * for struct am7xxx_header
  */
 #define AM7XXX_HEADER_WIRE_SIZE 24
  * for struct am7xxx_header
  */
 #define AM7XXX_HEADER_WIRE_SIZE 24
@@ -55,11 +78,13 @@ static struct am7xxx_usb_device_descriptor supported_devices[] = {
 struct _am7xxx_device {
        libusb_device_handle *usb_device;
        uint8_t buffer[AM7XXX_HEADER_WIRE_SIZE];
 struct _am7xxx_device {
        libusb_device_handle *usb_device;
        uint8_t buffer[AM7XXX_HEADER_WIRE_SIZE];
+       am7xxx_context *ctx;
        am7xxx_device *next;
 };
 
 struct _am7xxx_context {
        libusb_context *usb_context;
        am7xxx_device *next;
 };
 
 struct _am7xxx_context {
        libusb_context *usb_context;
+       int log_level;
        am7xxx_device *devices_list;
 };
 
        am7xxx_device *devices_list;
 };
 
@@ -122,71 +147,72 @@ struct am7xxx_header {
 };
 
 
 };
 
 
-static void dump_devinfo_header(struct am7xxx_devinfo_header *d)
+#ifdef DEBUG
+static void debug_dump_devinfo_header(am7xxx_context *ctx, struct am7xxx_devinfo_header *d)
 {
 {
-       if (d == NULL)
+       if (ctx == NULL || d == NULL)
                return;
 
                return;
 
-       printf("Info header:\n");
-       printf("\tnative_width:  0x%08x (%u)\n", d->native_width, d->native_width);
-       printf("\tnative_height: 0x%08x (%u)\n", d->native_height, d->native_height);
-       printf("\tunknown0:      0x%08x (%u)\n", d->unknown0, d->unknown0);
-       printf("\tunknown1:      0x%08x (%u)\n", d->unknown1, d->unknown1);
+       debug(ctx, "Info header:\n");
+       debug(ctx, "\tnative_width:  0x%08x (%u)\n", d->native_width, d->native_width);
+       debug(ctx, "\tnative_height: 0x%08x (%u)\n", d->native_height, d->native_height);
+       debug(ctx, "\tunknown0:      0x%08x (%u)\n", d->unknown0, d->unknown0);
+       debug(ctx, "\tunknown1:      0x%08x (%u)\n", d->unknown1, d->unknown1);
 }
 
 }
 
-static void dump_image_header(struct am7xxx_image_header *i)
+static void debug_dump_image_header(am7xxx_context *ctx, struct am7xxx_image_header *i)
 {
 {
-       if (i == NULL)
+       if (ctx == NULL || i == NULL)
                return;
 
                return;
 
-       printf("Image header:\n");
-       printf("\tformat:     0x%08x (%u)\n", i->format, i->format);
-       printf("\twidth:      0x%08x (%u)\n", i->width, i->width);
-       printf("\theight:     0x%08x (%u)\n", i->height, i->height);
-       printf("\timage size: 0x%08x (%u)\n", i->image_size, i->image_size);
+       debug(ctx, "Image header:\n");
+       debug(ctx, "\tformat:     0x%08x (%u)\n", i->format, i->format);
+       debug(ctx, "\twidth:      0x%08x (%u)\n", i->width, i->width);
+       debug(ctx, "\theight:     0x%08x (%u)\n", i->height, i->height);
+       debug(ctx, "\timage size: 0x%08x (%u)\n", i->image_size, i->image_size);
 }
 
 }
 
-static void dump_power_header(struct am7xxx_power_header *p)
+static void debug_dump_power_header(am7xxx_context *ctx, struct am7xxx_power_header *p)
 {
 {
-       if (p == NULL)
+       if (ctx == NULL || p == NULL)
                return;
 
                return;
 
-       printf("Power header:\n");
-       printf("\tbit2: 0x%08x (%u)\n", p->bit2, p->bit2);
-       printf("\tbit1: 0x%08x (%u)\n", p->bit1, p->bit1);
-       printf("\tbit0: 0x%08x (%u)\n", p->bit0, p->bit0);
+       debug(ctx, "Power header:\n");
+       debug(ctx, "\tbit2: 0x%08x (%u)\n", p->bit2, p->bit2);
+       debug(ctx, "\tbit1: 0x%08x (%u)\n", p->bit1, p->bit1);
+       debug(ctx, "\tbit0: 0x%08x (%u)\n", p->bit0, p->bit0);
 }
 
 }
 
-static void dump_header(struct am7xxx_header *h)
+static void debug_dump_header(am7xxx_context *ctx, struct am7xxx_header *h)
 {
 {
-       if (h == NULL)
+       if (ctx == NULL || h == NULL)
                return;
 
                return;
 
-       printf("packet_type:     0x%08x (%u)\n", h->packet_type, h->packet_type);
-       printf("unknown0:        0x%02hhx (%hhu)\n", h->unknown0, h->unknown0);
-       printf("header_data_len: 0x%02hhx (%hhu)\n", h->header_data_len, h->header_data_len);
-       printf("unknown2:        0x%02hhx (%hhu)\n", h->unknown2, h->unknown2);
-       printf("unknown3:        0x%02hhx (%hhu)\n", h->unknown3, h->unknown3);
+       debug(ctx, "BEGIN\n");
+       debug(ctx, "packet_type:     0x%08x (%u)\n", h->packet_type, h->packet_type);
+       debug(ctx, "unknown0:        0x%02hhx (%hhu)\n", h->unknown0, h->unknown0);
+       debug(ctx, "header_data_len: 0x%02hhx (%hhu)\n", h->header_data_len, h->header_data_len);
+       debug(ctx, "unknown2:        0x%02hhx (%hhu)\n", h->unknown2, h->unknown2);
+       debug(ctx, "unknown3:        0x%02hhx (%hhu)\n", h->unknown3, h->unknown3);
 
        switch(h->packet_type) {
        case AM7XXX_PACKET_TYPE_DEVINFO:
 
        switch(h->packet_type) {
        case AM7XXX_PACKET_TYPE_DEVINFO:
-               dump_devinfo_header(&(h->header_data.devinfo));
+               debug_dump_devinfo_header(ctx, &(h->header_data.devinfo));
                break;
 
        case AM7XXX_PACKET_TYPE_IMAGE:
                break;
 
        case AM7XXX_PACKET_TYPE_IMAGE:
-               dump_image_header(&(h->header_data.image));
+               debug_dump_image_header(ctx, &(h->header_data.image));
                break;
 
        case AM7XXX_PACKET_TYPE_POWER:
                break;
 
        case AM7XXX_PACKET_TYPE_POWER:
-               dump_power_header(&(h->header_data.power));
+               debug_dump_power_header(ctx, &(h->header_data.power));
                break;
 
        default:
                break;
 
        default:
-               printf("Packet type not supported!\n");
+               debug(ctx, "Packet type not supported!\n");
                break;
        }
                break;
        }
-
-       fflush(stdout);
+       debug(ctx, "END\n\n");
 }
 
 static inline unsigned int in_80chars(unsigned int i)
 }
 
 static inline unsigned int in_80chars(unsigned int i)
@@ -196,18 +222,39 @@ static inline unsigned int in_80chars(unsigned int i)
        return ((i+1) % (80/3));
 }
 
        return ((i+1) % (80/3));
 }
 
-static void dump_buffer(uint8_t *buffer, unsigned int len)
+static void trace_dump_buffer(am7xxx_context *ctx, const char *message,
+                             uint8_t *buffer, unsigned int len)
 {
        unsigned int i;
 
 {
        unsigned int i;
 
-       if (buffer == NULL || len == 0)
+       if (ctx == NULL || buffer == NULL || len == 0)
                return;
 
                return;
 
+       trace(ctx, "\n");
+       if (message)
+               trace(ctx, "%s\n", message);
+
        for (i = 0; i < len; i++) {
        for (i = 0; i < len; i++) {
-               printf("%02hhX%c", buffer[i], (in_80chars(i) && (i < len - 1)) ? ' ' : '\n');
+               trace(ctx, "%02hhX%c", buffer[i], (in_80chars(i) && (i < len - 1)) ? ' ' : '\n');
        }
        }
-       fflush(stdout);
+       trace(ctx, "\n");
 }
 }
+#else
+static void debug_dump_header(am7xxx_context *ctx, struct am7xxx_header *h)
+{
+       (void)ctx;
+       (void)h;
+}
+
+static void trace_dump_buffer(am7xxx_context *ctx, const char *message,
+                             uint8_t *buffer, unsigned int len)
+{
+       (void)ctx;
+       (void)message;
+       (void)buffer;
+       (void)len;
+}
+#endif /* DEBUG */
 
 static int read_data(am7xxx_device *dev, uint8_t *buffer, unsigned int len)
 {
 
 static int read_data(am7xxx_device *dev, uint8_t *buffer, unsigned int len)
 {
@@ -216,16 +263,12 @@ static int read_data(am7xxx_device *dev, uint8_t *buffer, unsigned int len)
 
        ret = libusb_bulk_transfer(dev->usb_device, 0x81, buffer, len, &transferred, 0);
        if (ret != 0 || (unsigned int)transferred != len) {
 
        ret = libusb_bulk_transfer(dev->usb_device, 0x81, buffer, len, &transferred, 0);
        if (ret != 0 || (unsigned int)transferred != len) {
-               fprintf(stderr, "Error: ret: %d\ttransferred: %d (expected %u)\n",
-                       ret, transferred, len);
+               error(dev->ctx, "ret: %d\ttransferred: %d (expected %u)\n",
+                     ret, transferred, len);
                return ret;
        }
 
                return ret;
        }
 
-#if DEBUG
-       printf("\n<-- received\n");
-       dump_buffer(buffer, len);
-       printf("\n");
-#endif
+       trace_dump_buffer(dev->ctx, "<-- received", buffer, len);
 
        return 0;
 }
 
        return 0;
 }
@@ -235,16 +278,12 @@ static int send_data(am7xxx_device *dev, uint8_t *buffer, unsigned int len)
        int ret;
        int transferred = 0;
 
        int ret;
        int transferred = 0;
 
-#if DEBUG
-       printf("\nsending -->\n");
-       dump_buffer(buffer, len);
-       printf("\n");
-#endif
+       trace_dump_buffer(dev->ctx, "sending -->", buffer, len);
 
        ret = libusb_bulk_transfer(dev->usb_device, 1, buffer, len, &transferred, 0);
        if (ret != 0 || (unsigned int)transferred != len) {
 
        ret = libusb_bulk_transfer(dev->usb_device, 1, buffer, len, &transferred, 0);
        if (ret != 0 || (unsigned int)transferred != len) {
-               fprintf(stderr, "Error: ret: %d\ttransferred: %d (expected %u)\n",
-                       ret, transferred, len);
+               error(dev->ctx, "ret: %d\ttransferred: %d (expected %u)\n",
+                     ret, transferred, len);
                return ret;
        }
 
                return ret;
        }
 
@@ -291,11 +330,7 @@ static int read_header(am7xxx_device *dev, struct am7xxx_header *h)
 
        unserialize_header(dev->buffer, h);
 
 
        unserialize_header(dev->buffer, h);
 
-#if DEBUG
-       printf("\n");
-       dump_header(h);
-       printf("\n");
-#endif
+       debug_dump_header(dev->ctx, h);
 
        ret = 0;
 
 
        ret = 0;
 
@@ -307,31 +342,66 @@ static int send_header(am7xxx_device *dev, struct am7xxx_header *h)
 {
        int ret;
 
 {
        int ret;
 
-#if DEBUG
-       printf("\n");
-       dump_header(h);
-       printf("\n");
-#endif
+       debug_dump_header(dev->ctx, h);
 
        serialize_header(h, dev->buffer);
        ret = send_data(dev, dev->buffer, AM7XXX_HEADER_WIRE_SIZE);
        if (ret < 0)
 
        serialize_header(h, dev->buffer);
        ret = send_data(dev, dev->buffer, AM7XXX_HEADER_WIRE_SIZE);
        if (ret < 0)
-               fprintf(stderr, "send_header: failed to send data.\n");
+               error(dev->ctx, "failed to send data\n");
 
        return ret;
 }
 
 
        return ret;
 }
 
-static am7xxx_device *add_new_device(am7xxx_device **devices_list)
+/* When level == AM7XXX_LOG_FATAL do not check the log_level from the context
+ * and print the message unconditionally, this makes it possible to print
+ * fatal messages even early on initialization, before the context has been
+ * set up */
+static void log_message(am7xxx_context *ctx,
+                       int level,
+                       const char *function,
+                       int line,
+                       const char *fmt,
+                       ...)
+{
+       va_list ap;
+
+       if (level == AM7XXX_LOG_FATAL || (ctx && level <= ctx->log_level)) {
+               if (function) {
+                       fprintf(stderr, "%s", function);
+                       if (line)
+                               fprintf(stderr, "[%d]", line);
+                       fprintf(stderr, ": ");
+               }
+
+               va_start(ap, fmt);
+               vfprintf(stderr, fmt, ap);
+               va_end(ap);
+       }
+
+       return;
+}
+
+static am7xxx_device *add_new_device(am7xxx_context *ctx)
 {
 {
+       am7xxx_device **devices_list;
        am7xxx_device *new_device;
 
        am7xxx_device *new_device;
 
+       if (ctx == NULL) {
+               fatal("context must not be NULL!\n");
+               return NULL;
+       }
+
+       devices_list = &(ctx->devices_list);
+
        new_device = malloc(sizeof(*new_device));
        if (new_device == NULL) {
        new_device = malloc(sizeof(*new_device));
        if (new_device == NULL) {
-               perror("malloc");
+               fatal("cannot allocate a new device (%s)\n", strerror(errno));
                return NULL;
        }
        memset(new_device, 0, sizeof(*new_device));
 
                return NULL;
        }
        memset(new_device, 0, sizeof(*new_device));
 
+       new_device->ctx = ctx;
+
        if (*devices_list == NULL) {
                *devices_list = new_device;
        } else {
        if (*devices_list == NULL) {
                *devices_list = new_device;
        } else {
@@ -343,12 +413,18 @@ static am7xxx_device *add_new_device(am7xxx_device **devices_list)
        return new_device;
 }
 
        return new_device;
 }
 
-static am7xxx_device *find_device(am7xxx_device *devices_list,
+static am7xxx_device *find_device(am7xxx_context *ctx,
                                  unsigned int device_index)
 {
        unsigned int i = 0;
                                  unsigned int device_index)
 {
        unsigned int i = 0;
-       am7xxx_device *current = devices_list;
+       am7xxx_device *current;
 
 
+       if (ctx == NULL) {
+               fatal("context must not be NULL!\n");
+               return NULL;
+       }
+
+       current = ctx->devices_list;
        while (current && i++ < device_index)
                current = current->next;
 
        while (current && i++ < device_index)
                current = current->next;
 
@@ -371,7 +447,7 @@ typedef enum {
  * device with index 'open_device_index' and returns the correspondent
  * am7xxx_device in the 'dev' parameter; the function returns 0 on success,
  * 1 if the device was already open and a negative value on error.
  * device with index 'open_device_index' and returns the correspondent
  * am7xxx_device in the 'dev' parameter; the function returns 0 on success,
  * 1 if the device was already open and a negative value on error.
- * 
+ *
  * NOTES:
  * if scan_devices() fails when called with 'op' == SCAN_OP_BUILD_DEVLIST,
  * the caller might want to call am7xxx_shutdown() in order to remove
  * NOTES:
  * if scan_devices() fails when called with 'op' == SCAN_OP_BUILD_DEVLIST,
  * the caller might want to call am7xxx_shutdown() in order to remove
@@ -387,11 +463,11 @@ static int scan_devices(am7xxx_context *ctx, scan_op op,
        int ret;
 
        if (ctx == NULL) {
        int ret;
 
        if (ctx == NULL) {
-               fprintf(stderr, "%s: context must not be NULL!\n", __func__);
+               fatal("context must not be NULL!\n");
                return -EINVAL;
        }
        if (op == SCAN_OP_BUILD_DEVLIST && ctx->devices_list != NULL) {
                return -EINVAL;
        }
        if (op == SCAN_OP_BUILD_DEVLIST && ctx->devices_list != NULL) {
-               fprintf(stderr, "%s: device scan done already? Abort!\n", __func__);
+               error(ctx, "device scan done already? Abort!\n");
                return -EINVAL;
        }
 
                return -EINVAL;
        }
 
@@ -416,24 +492,24 @@ static int scan_devices(am7xxx_context *ctx, scan_op op,
 
                                if (op == SCAN_OP_BUILD_DEVLIST) {
                                        am7xxx_device *new_device;
 
                                if (op == SCAN_OP_BUILD_DEVLIST) {
                                        am7xxx_device *new_device;
-                                       /* debug */
-                                       printf("am7xxx device found, index: %d, name: %s\n",
-                                              current_index,
-                                              supported_devices[j].name);
-                                       new_device = add_new_device(&(ctx->devices_list));
+                                       info(ctx, "am7xxx device found, index: %d, name: %s\n",
+                                            current_index,
+                                            supported_devices[j].name);
+                                       new_device = add_new_device(ctx);
                                        if (new_device == NULL) {
                                                /* XXX, the caller may want
                                                 * to call am7xxx_shutdown() if
                                                 * we fail here, as we may have
                                                 * added some devices already
                                                 */
                                        if (new_device == NULL) {
                                                /* XXX, the caller may want
                                                 * to call am7xxx_shutdown() if
                                                 * we fail here, as we may have
                                                 * added some devices already
                                                 */
+                                               debug(ctx, "Cannot create a new device\n");
                                                ret = -ENODEV;
                                                goto out;
                                        }
                                } else if (op == SCAN_OP_OPEN_DEVICE &&
                                           current_index == open_device_index) {
 
                                                ret = -ENODEV;
                                                goto out;
                                        }
                                } else if (op == SCAN_OP_OPEN_DEVICE &&
                                           current_index == open_device_index) {
 
-                                       *dev = find_device(ctx->devices_list, open_device_index);
+                                       *dev = find_device(ctx, open_device_index);
                                        if (*dev == NULL) {
                                                ret = -ENODEV;
                                                goto out;
                                        if (*dev == NULL) {
                                                ret = -ENODEV;
                                                goto out;
@@ -441,13 +517,16 @@ static int scan_devices(am7xxx_context *ctx, scan_op op,
 
                                        /* the usb device has already been opened */
                                        if ((*dev)->usb_device) {
 
                                        /* the usb device has already been opened */
                                        if ((*dev)->usb_device) {
+                                               debug(ctx, "(*dev)->usb_device already set\n");
                                                ret = 1;
                                                goto out;
                                        }
 
                                        ret = libusb_open(list[i], &((*dev)->usb_device));
                                                ret = 1;
                                                goto out;
                                        }
 
                                        ret = libusb_open(list[i], &((*dev)->usb_device));
-                                       if (ret < 0)
+                                       if (ret < 0) {
+                                               debug(ctx, "libusb_open failed\n");
                                                goto out;
                                                goto out;
+                                       }
 
                                        libusb_set_configuration((*dev)->usb_device, 1);
                                        libusb_claim_interface((*dev)->usb_device, 0);
 
                                        libusb_set_configuration((*dev)->usb_device, 1);
                                        libusb_claim_interface((*dev)->usb_device, 0);
@@ -460,6 +539,7 @@ static int scan_devices(am7xxx_context *ctx, scan_op op,
 
        /* if we made it up to here we didn't find any device to open */
        if (op == SCAN_OP_OPEN_DEVICE) {
 
        /* if we made it up to here we didn't find any device to open */
        if (op == SCAN_OP_OPEN_DEVICE) {
+               error(ctx, "Cannot find any device to open\n");
                ret = -ENODEV;
                goto out;
        }
                ret = -ENODEV;
                goto out;
        }
@@ -477,12 +557,15 @@ int am7xxx_init(am7xxx_context **ctx)
 
        *ctx = malloc(sizeof(**ctx));
        if (*ctx == NULL) {
 
        *ctx = malloc(sizeof(**ctx));
        if (*ctx == NULL) {
-               perror("malloc");
+               fatal("cannot allocate the context (%s)\n", strerror(errno));
                ret = -ENOMEM;
                goto out;
        }
        memset(*ctx, 0, sizeof(**ctx));
 
                ret = -ENOMEM;
                goto out;
        }
        memset(*ctx, 0, sizeof(**ctx));
 
+       /* Set the highest log level during initialization */
+       (*ctx)->log_level = AM7XXX_LOG_TRACE;
+
        ret = libusb_init(&((*ctx)->usb_context));
        if (ret < 0)
                goto out_free_context;
        ret = libusb_init(&((*ctx)->usb_context));
        if (ret < 0)
                goto out_free_context;
@@ -491,11 +574,13 @@ int am7xxx_init(am7xxx_context **ctx)
 
        ret = scan_devices(*ctx, SCAN_OP_BUILD_DEVLIST , 0, NULL);
        if (ret < 0) {
 
        ret = scan_devices(*ctx, SCAN_OP_BUILD_DEVLIST , 0, NULL);
        if (ret < 0) {
-               fprintf(stderr, "%s: scan_devices failed\n", __func__);
+               error(*ctx, "scan_devices() failed\n");
                am7xxx_shutdown(*ctx);
                goto out;
        }
 
                am7xxx_shutdown(*ctx);
                goto out;
        }
 
+       /* Set a quieter log level as default for normal operation */
+       (*ctx)->log_level = AM7XXX_LOG_ERROR;
        return 0;
 
 out_free_context:
        return 0;
 
 out_free_context:
@@ -510,7 +595,7 @@ void am7xxx_shutdown(am7xxx_context *ctx)
        am7xxx_device *current;
 
        if (ctx == NULL) {
        am7xxx_device *current;
 
        if (ctx == NULL) {
-               fprintf(stderr, "%s: context must not be NULL!\n", __func__);
+               fatal("context must not be NULL!\n");
                return;
        }
 
                return;
        }
 
@@ -527,13 +612,18 @@ void am7xxx_shutdown(am7xxx_context *ctx)
        ctx = NULL;
 }
 
        ctx = NULL;
 }
 
+void am7xxx_set_log_level(am7xxx_context *ctx, am7xxx_log_level log_level)
+{
+       ctx->log_level = log_level;
+}
+
 int am7xxx_open_device(am7xxx_context *ctx, am7xxx_device **dev,
                       unsigned int device_index)
 {
        int ret;
 
        if (ctx == NULL) {
 int am7xxx_open_device(am7xxx_context *ctx, am7xxx_device **dev,
                       unsigned int device_index)
 {
        int ret;
 
        if (ctx == NULL) {
-               fprintf(stderr, "%s: context must not be NULL!\n", __func__);
+               fatal("context must not be NULL!\n");
                return -EINVAL;
        }
 
                return -EINVAL;
        }
 
@@ -541,8 +631,7 @@ int am7xxx_open_device(am7xxx_context *ctx, am7xxx_device **dev,
        if (ret < 0) {
                errno = ENODEV;
        } else if (ret > 0) {
        if (ret < 0) {
                errno = ENODEV;
        } else if (ret > 0) {
-               /* warning */
-               fprintf(stderr, "%s: device %d already open\n", __func__, device_index);
+               warning(ctx, "device %d already open\n", device_index);
                errno = EBUSY;
                ret = -EBUSY;
        }
                errno = EBUSY;
                ret = -EBUSY;
        }
@@ -553,7 +642,7 @@ int am7xxx_open_device(am7xxx_context *ctx, am7xxx_device **dev,
 int am7xxx_close_device(am7xxx_device *dev)
 {
        if (dev == NULL) {
 int am7xxx_close_device(am7xxx_device *dev)
 {
        if (dev == NULL) {
-               fprintf(stderr, "%s: dev must not be NULL!\n", __func__);
+               fatal("dev must not be NULL!\n");
                return -EINVAL;
        }
        if (dev->usb_device) {
                return -EINVAL;
        }
        if (dev->usb_device) {
@@ -565,10 +654,7 @@ int am7xxx_close_device(am7xxx_device *dev)
 }
 
 int am7xxx_get_device_info(am7xxx_device *dev,
 }
 
 int am7xxx_get_device_info(am7xxx_device *dev,
-                          unsigned int *native_width,
-                          unsigned int *native_height,
-                          unsigned int *unknown0,
-                          unsigned int *unknown1)
+                          am7xxx_device_info *device_info)
 {
        int ret;
        struct am7xxx_header h = {
 {
        int ret;
        struct am7xxx_header h = {
@@ -595,10 +681,75 @@ int am7xxx_get_device_info(am7xxx_device *dev,
        if (ret < 0)
                return ret;
 
        if (ret < 0)
                return ret;
 
-       *native_width = h.header_data.devinfo.native_width;
-       *native_height = h.header_data.devinfo.native_height;
-       *unknown0 = h.header_data.devinfo.unknown0;
-       *unknown1 = h.header_data.devinfo.unknown1;
+       device_info->native_width = h.header_data.devinfo.native_width;
+       device_info->native_height = h.header_data.devinfo.native_height;
+#if 0
+       /* No reason to expose these in the public API until we know what they mean */
+       device_info->unknown0 = h.header_data.devinfo.unknown0;
+       device_info->unknown1 = h.header_data.devinfo.unknown1;
+#endif
+
+       return 0;
+}
+
+int am7xxx_calc_scaled_image_dimensions(am7xxx_device *dev,
+                                       unsigned int upscale,
+                                       unsigned int original_width,
+                                       unsigned int original_height,
+                                       unsigned int *scaled_width,
+                                       unsigned int *scaled_height)
+{
+
+       am7xxx_device_info device_info;
+       float width_ratio;
+       float height_ratio;
+       int ret;
+
+       ret = am7xxx_get_device_info(dev, &device_info);
+       if (ret < 0) {
+               error(dev->ctx, "cannot get device info\n");
+               return ret;
+       }
+
+       /*
+        * Check if we need to rescale; if the input image fits the native
+        * dimensions there is no need to, unless we want to upscale.
+        */
+       if (!upscale &&
+           original_width <= device_info.native_width &&
+           original_height <= device_info.native_height ) {
+               debug(dev->ctx, "CASE 0, no rescaling, the original image fits already\n");
+               *scaled_width = original_width;
+               *scaled_height = original_height;
+               return 0;
+       }
+
+       /* Input dimensions relative to the device native dimensions */
+       width_ratio =  (float)original_width / device_info.native_width;
+       height_ratio = (float)original_height / device_info.native_height;
+
+       if (width_ratio > height_ratio) {
+               /*
+                * The input is proportionally "wider" than the device viewport
+                * so its height needs to be adjusted
+                */
+               debug(dev->ctx, "CASE 1, original image wider, adjust the scaled height\n");
+               *scaled_width = device_info.native_width;
+               *scaled_height = (unsigned int)lroundf(original_height / width_ratio);
+       } else if (width_ratio < height_ratio) {
+               /*
+                * The input is proportionally "taller" than the device viewport
+                * so its width needs to be adjusted
+                */
+               debug(dev->ctx, "CASE 2 original image taller, adjust the scaled width\n");
+               *scaled_width = (unsigned int)lroundf(original_width / height_ratio);
+               *scaled_height = device_info.native_height;
+       } else {
+               debug(dev->ctx, "CASE 3, just rescale, same aspect ratio already\n");
+               *scaled_width = device_info.native_width;
+               *scaled_height = device_info.native_height;
+       }
+       debug(dev->ctx, "scaled dimensions: %dx%d\n", *scaled_width, *scaled_height);
 
        return 0;
 }
 
        return 0;
 }
@@ -608,7 +759,7 @@ int am7xxx_send_image(am7xxx_device *dev,
                      unsigned int width,
                      unsigned int height,
                      uint8_t *image,
                      unsigned int width,
                      unsigned int height,
                      uint8_t *image,
-                     unsigned int size)
+                     unsigned int image_size)
 {
        int ret;
        struct am7xxx_header h = {
 {
        int ret;
        struct am7xxx_header h = {
@@ -622,7 +773,7 @@ int am7xxx_send_image(am7xxx_device *dev,
                                .format     = format,
                                .width      = width,
                                .height     = height,
                                .format     = format,
                                .width      = width,
                                .height     = height,
-                               .image_size = size,
+                               .image_size = image_size,
                        },
                },
        };
                        },
                },
        };
@@ -631,10 +782,12 @@ int am7xxx_send_image(am7xxx_device *dev,
        if (ret < 0)
                return ret;
 
        if (ret < 0)
                return ret;
 
-       if (image == NULL || size == 0)
+       if (image == NULL || image_size == 0) {
+               warning(dev->ctx, "Not sending any data, check the 'image' or 'image_size' parameters\n");
                return 0;
                return 0;
+       }
 
 
-       return send_data(dev, image, size);
+       return send_data(dev, image, image_size);
 }
 
 int am7xxx_set_power_mode(am7xxx_device *dev, am7xxx_power_mode mode)
 }
 
 int am7xxx_set_power_mode(am7xxx_device *dev, am7xxx_power_mode mode)
@@ -679,7 +832,7 @@ int am7xxx_set_power_mode(am7xxx_device *dev, am7xxx_power_mode mode)
                break;
 
        default:
                break;
 
        default:
-               fprintf(stderr, "Unsupported power mode.\n");
+               error(dev->ctx, "Power mode not supported!\n");
                return -EINVAL;
        };
 
                return -EINVAL;
        };