[FFmpeg-devel] [PATCH] lavd/v4l2: sanitize logic of device_try_init(), so that it properly signal errors

[Stefano Sabatini]

Make device_try_init() return an error value, and allow to properly
report errors which are not due to a wrong pixel/codec configuration.

In particular, report intelligible feedback in case of busy device.
---
 libavdevice/v4l2.c |   64 ++++++++++++++++++++++++++++------------------------
 1 file changed, 34 insertions(+), 30 deletions(-)

diff --git a/libavdevice/v4l2.c b/libavdevice/v4l2.c
index f5940ad..8387011 100644
--- a/libavdevice/v4l2.c
+++ b/libavdevice/v4l2.c
@@ -742,19 +742,25 @@ static int v4l2_set_parameters(AVFormatContext *s1)
     return 0;
 }
 
-static uint32_t device_try_init(AVFormatContext *s1,
-                                enum AVPixelFormat pix_fmt,
-                                int *width,
-                                int *height,
-                                enum AVCodecID *codec_id)
+static int device_try_init(AVFormatContext *s1,
+                           enum AVPixelFormat pix_fmt,
+                           int *width,
+                           int *height,
+                           uint32_t *desired_format,
+                           enum AVCodecID *codec_id)
 {
-    uint32_t desired_format = fmt_ff2v4l(pix_fmt, s1->video_codec_id);
+    int ret, i;
 
-    if (desired_format == 0 ||
-        device_init(s1, width, height, desired_format) < 0) {
-        int i;
+    *desired_format = fmt_ff2v4l(pix_fmt, s1->video_codec_id);
 
-        desired_format = 0;
+    if (*desired_format) {
+        ret = device_init(s1, width, height, *desired_format);
+        if (ret >= 0 || ret != AVERROR(EINVAL))
+            return ret;
+    }
+
+    /* todo REINDENT */
+        *desired_format = 0;
         for (i = 0; i<FF_ARRAY_ELEMS(fmt_conversion_table); i++) {
             if (s1->video_codec_id == AV_CODEC_ID_NONE ||
                 fmt_conversion_table[i].codec_id == s1->video_codec_id) {
@@ -762,21 +768,26 @@ static uint32_t device_try_init(AVFormatContext *s1,
                        avcodec_get_name(fmt_conversion_table[i].codec_id),
                        (char *)av_x_if_null(av_get_pix_fmt_name(fmt_conversion_table[i].ff_fmt), "none"));
 
-                desired_format = fmt_conversion_table[i].v4l2_fmt;
-                if (device_init(s1, width, height, desired_format) >= 0) {
+                *desired_format = fmt_conversion_table[i].v4l2_fmt;
+                ret = device_init(s1, width, height, *desired_format);
+                if (ret >= 0 || ret != AVERROR(EINVAL))
                     break;
-                }
-                desired_format = 0;
+                *desired_format = 0;
             }
         }
-    }
 
-    if (desired_format != 0) {
-        *codec_id = fmt_v4l2codec(desired_format);
+    if (*desired_format == 0) {
+        av_log(s1, AV_LOG_ERROR, "Cannot find a proper format for "
+               "codec '%s' (id %d), pixel format '%s' (id %d)\n",
+               avcodec_get_name(s1->video_codec_id), s1->video_codec_id,
+               (char *)av_x_if_null(av_get_pix_fmt_name(pix_fmt), "none"), pix_fmt);
+        ret = AVERROR(EINVAL);
+    } else {
+        *codec_id = fmt_v4l2codec(*desired_format);
         av_assert0(*codec_id != AV_CODEC_ID_NONE);
     }
 
-    return desired_format;
+    return ret;
 }
 
 static int v4l2_read_header(AVFormatContext *s1)
@@ -844,8 +855,11 @@ static int v4l2_read_header(AVFormatContext *s1)
                "Setting frame size to %dx%d\n", s->width, s->height);
     }
 
-    desired_format = device_try_init(s1, pix_fmt, &s->width, &s->height,
-                                     &codec_id);
+    res = device_try_init(s1, pix_fmt, &s->width, &s->height, &desired_format, &codec_id);
+    if (res < 0) {
+        v4l2_close(s->fd);
+        goto out;
+    }
 
     /* If no pixel_format was specified, the codec_id was not known up
      * until now. Set video_codec_id in the context, as codec_id will
@@ -854,16 +868,6 @@ static int v4l2_read_header(AVFormatContext *s1)
     if (codec_id != AV_CODEC_ID_NONE && s1->video_codec_id == AV_CODEC_ID_NONE)
         s1->video_codec_id = codec_id;
 
-    if (desired_format == 0) {
-        av_log(s1, AV_LOG_ERROR, "Cannot find a proper format for "
-               "codec '%s' (id %d), pixel format '%s' (id %d)\n",
-               avcodec_get_name(s1->video_codec_id), s1->video_codec_id,
-               (char *)av_x_if_null(av_get_pix_fmt_name(pix_fmt), "none"), pix_fmt);
-        v4l2_close(s->fd);
-
-        res = AVERROR(EIO);
-        goto out;
-    }
     if ((res = av_image_check_size(s->width, s->height, 0, s1)) < 0)
         goto out;
 
-- 
1.7.9.5