[media] v4l2: use __u32 rather than enums in ioctl() structs

V4L2 uses the enum type in IOCTL arguments in IOCTLs that were defined until
the use of enum was considered less than ideal. Recently Rémi Denis-Courmont
brought up the issue by proposing a patch to convert the enums to unsigned:

<URL:http://www.spinics.net/lists/linux-media/msg46167.html>

This sparked a long discussion where another solution to the issue was
proposed: two sets of IOCTL structures, one with __u32 and the other with
enums, and conversion code between the two:

<URL:http://www.spinics.net/lists/linux-media/msg47168.html>

Both approaches implement a complete solution that resolves the problem. The
first one is simple but requires assuming enums and __u32 are the same in
size (so we won't break the ABI) while the second one is more complex and
less clean but does not require making that assumption.

The issue boils down to whether enums are fundamentally different from __u32
or not, and can the former be substituted by the latter. During the
discussion it was concluded that the __u32 has the same size as enums on all
archs Linux is supported: it has not been shown that replacing those enums
in IOCTL arguments would break neither source or binary compatibility. If no
such reason is found, just replacing the enums with __u32s is the way to go.

This is what this patch does. This patch is slightly different from Remi's
first RFC (link above): it uses __u32 instead of unsigned and also changes
the arguments of VIDIOC_G_PRIORITY and VIDIOC_S_PRIORITY.

Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>
Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 33 insertions, 31 deletions

diff --git a/include/linux/videodev2.h b/include/linux/videodev2.h
index 5a09ac3f7683..ace8ac000b9b 100644
--- a/include/linux/videodev2.h
+++ b/include/linux/videodev2.h
@@ -292,10 +292,10 @@ struct v4l2_pix_format {
         __u32                   width;
         __u32                   height;
         __u32                   pixelformat;
-        enum v4l2_field         field;
+        __u32                   field;          /* enum v4l2_field */
         __u32                   bytesperline;   /* for padding, zero if unused */
         __u32                   sizeimage;
-        enum v4l2_colorspace    colorspace;
+        __u32                   colorspace;     /* enum v4l2_colorspace */
         __u32                   priv;           /* private data, depends on pixelformat */
 };
 
@@ -432,7 +432,7 @@ struct v4l2_pix_format {
  */
 struct v4l2_fmtdesc {
         __u32               index;             /* Format number      */
-        enum v4l2_buf_type  type;              /* buffer type        */
+        __u32               type;              /* enum v4l2_buf_type */
         __u32               flags;
         __u8                description[32];   /* Description string */
         __u32               pixelformat;       /* Format fourcc      */
@@ -573,8 +573,8 @@ struct v4l2_jpegcompression {
  */
 struct v4l2_requestbuffers {
         __u32                   count;
-        enum v4l2_buf_type      type;
-        enum v4l2_memory        memory;
+        __u32                   type;           /* enum v4l2_buf_type */
+        __u32                   memory;         /* enum v4l2_memory */
         __u32                   reserved[2];
 };
 
@@ -610,15 +610,17 @@ struct v4l2_plane {
 /**
  * struct v4l2_buffer - video buffer info
  * @index:      id number of the buffer
- * @type:       buffer type (type == *_MPLANE for multiplanar buffers)
+ * @type:       enum v4l2_buf_type; buffer type (type == *_MPLANE for
+ *              multiplanar buffers);
  * @bytesused:  number of bytes occupied by data in the buffer (payload);
  *              unused (set to 0) for multiplanar buffers
  * @flags:      buffer informational flags
- * @field:      field order of the image in the buffer
+ * @field:      enum v4l2_field; field order of the image in the buffer
  * @timestamp:  frame timestamp
  * @timecode:   frame timecode
  * @sequence:   sequence count of this frame
- * @memory:     the method, in which the actual video data is passed
+ * @memory:     enum v4l2_memory; the method, in which the actual video data is
+ *              passed
  * @offset:     for non-multiplanar buffers with memory == V4L2_MEMORY_MMAP;
  *              offset from the start of the device memory for this plane,
  *              (or a "cookie" that should be passed to mmap() as offset)
@@ -636,16 +638,16 @@ struct v4l2_plane {
  */
 struct v4l2_buffer {
         __u32                   index;
-        enum v4l2_buf_type      type;
+        __u32                   type;
         __u32                   bytesused;
         __u32                   flags;
-        enum v4l2_field         field;
+        __u32                   field;
         struct timeval          timestamp;
         struct v4l2_timecode    timecode;
         __u32                   sequence;
 
         /* memory location */
-        enum v4l2_memory        memory;
+        __u32                   memory;
         union {
                 __u32           offset;
                 unsigned long   userptr;
@@ -708,7 +710,7 @@ struct v4l2_clip {
 
 struct v4l2_window {
         struct v4l2_rect        w;
-        enum v4l2_field         field;
+        __u32                   field;   /* enum v4l2_field */
         __u32                   chromakey;
         struct v4l2_clip        __user *clips;
         __u32                   clipcount;
@@ -745,14 +747,14 @@ struct v4l2_outputparm {
  *      I N P U T   I M A G E   C R O P P I N G
  */
 struct v4l2_cropcap {
-        enum v4l2_buf_type      type;
+        __u32                   type;   /* enum v4l2_buf_type */
         struct v4l2_rect        bounds;
         struct v4l2_rect        defrect;
         struct v4l2_fract       pixelaspect;
 };
 
 struct v4l2_crop {
-        enum v4l2_buf_type      type;
+        __u32                   type;   /* enum v4l2_buf_type */
         struct v4l2_rect        c;
 };
 
@@ -1040,7 +1042,7 @@ struct v4l2_input {
         __u8         name[32];          /*  Label */
         __u32        type;              /*  Type of input */
         __u32        audioset;          /*  Associated audios (bitfield) */
-        __u32        tuner;             /*  Associated tuner */
+        __u32        tuner;             /*  enum v4l2_tuner_type */
         v4l2_std_id  std;
         __u32        status;
         __u32        capabilities;
@@ -1157,7 +1159,7 @@ enum v4l2_ctrl_type {
 /*  Used in the VIDIOC_QUERYCTRL ioctl for querying controls */
 struct v4l2_queryctrl {
         __u32                id;
-        enum v4l2_ctrl_type  type;
+        __u32                type;      /* enum v4l2_ctrl_type */
         __u8                 name[32];  /* Whatever */
         __s32                minimum;   /* Note signedness */
         __s32                maximum;
@@ -1792,7 +1794,7 @@ enum v4l2_jpeg_chroma_subsampling {
 struct v4l2_tuner {
         __u32                   index;
         __u8                    name[32];
-        enum v4l2_tuner_type    type;
+        __u32                   type;   /* enum v4l2_tuner_type */
         __u32                   capability;
         __u32                   rangelow;
         __u32                   rangehigh;
@@ -1842,14 +1844,14 @@ struct v4l2_modulator {
 
 struct v4l2_frequency {
         __u32                 tuner;
-        enum v4l2_tuner_type  type;
+        __u32                 type;     /* enum v4l2_tuner_type */
         __u32                 frequency;
         __u32                 reserved[8];
 };
 
 struct v4l2_hw_freq_seek {
         __u32                 tuner;
-        enum v4l2_tuner_type  type;
+        __u32                 type;     /* enum v4l2_tuner_type */
         __u32                 seek_upward;
         __u32                 wrap_around;
         __u32                 spacing;
@@ -2060,7 +2062,7 @@ struct v4l2_sliced_vbi_cap {
                                  (equals frame lines 313-336 for 625 line video
                                   standards, 263-286 for 525 line standards) */
         __u16   service_lines[2][24];
-        enum v4l2_buf_type type;
+        __u32   type;           /* enum v4l2_buf_type */
         __u32   reserved[3];    /* must be 0 */
 };
 
@@ -2141,8 +2143,8 @@ struct v4l2_plane_pix_format {
  * @width:              image width in pixels
  * @height:             image height in pixels
  * @pixelformat:        little endian four character code (fourcc)
- * @field:              field order (for interlaced video)
- * @colorspace:         supplemental to pixelformat
+ * @field:              enum v4l2_field; field order (for interlaced video)
+ * @colorspace:         enum v4l2_colorspace; supplemental to pixelformat
  * @plane_fmt:          per-plane information
  * @num_planes:         number of planes for this format
  */
@@ -2150,8 +2152,8 @@ struct v4l2_pix_format_mplane {
         __u32                           width;
         __u32                           height;
         __u32                           pixelformat;
-        enum v4l2_field                 field;
-        enum v4l2_colorspace            colorspace;
+        __u32                           field;
+        __u32                           colorspace;
 
         struct v4l2_plane_pix_format    plane_fmt[VIDEO_MAX_PLANES];
         __u8                            num_planes;
@@ -2160,7 +2162,7 @@ struct v4l2_pix_format_mplane {
 
 /**
  * struct v4l2_format - stream data format
- * @type:       type of the data stream
+ * @type:       enum v4l2_buf_type; type of the data stream
  * @pix:        definition of an image format
  * @pix_mp:     definition of a multiplanar image format
  * @win:        definition of an overlaid image
@@ -2169,7 +2171,7 @@ struct v4l2_pix_format_mplane {
  * @raw_data:   placeholder for future extensions and custom formats
  */
 struct v4l2_format {
-        enum v4l2_buf_type type;
+        __u32    type;
         union {
                 struct v4l2_pix_format          pix;     /* V4L2_BUF_TYPE_VIDEO_CAPTURE */
                 struct v4l2_pix_format_mplane   pix_mp;  /* V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE */
@@ -2183,7 +2185,7 @@ struct v4l2_format {
 /*      Stream type-dependent parameters
  */
 struct v4l2_streamparm {
-        enum v4l2_buf_type type;
+        __u32    type;                  /* enum v4l2_buf_type */
         union {
                 struct v4l2_captureparm capture;
                 struct v4l2_outputparm  output;
@@ -2296,14 +2298,14 @@ struct v4l2_dbg_chip_ident {
  * @index:      on return, index of the first created buffer
  * @count:      entry: number of requested buffers,
  *              return: number of created buffers
- * @memory:     buffer memory type
+ * @memory:     enum v4l2_memory; buffer memory type
  * @format:     frame format, for which buffers are requested
  * @reserved:   future extensions
  */
 struct v4l2_create_buffers {
         __u32                   index;
         __u32                   count;
-        enum v4l2_memory        memory;
+        __u32                   memory;
         struct v4l2_format      format;
         __u32                   reserved[8];
 };
@@ -2360,8 +2362,8 @@ struct v4l2_create_buffers {
 #define VIDIOC_TRY_FMT          _IOWR('V', 64, struct v4l2_format)
 #define VIDIOC_ENUMAUDIO        _IOWR('V', 65, struct v4l2_audio)
 #define VIDIOC_ENUMAUDOUT       _IOWR('V', 66, struct v4l2_audioout)
-#define VIDIOC_G_PRIORITY        _IOR('V', 67, enum v4l2_priority)
-#define VIDIOC_S_PRIORITY        _IOW('V', 68, enum v4l2_priority)
+#define VIDIOC_G_PRIORITY        _IOR('V', 67, __u32) /* enum v4l2_priority */
+#define VIDIOC_S_PRIORITY        _IOW('V', 68, __u32) /* enum v4l2_priority */
 #define VIDIOC_G_SLICED_VBI_CAP _IOWR('V', 69, struct v4l2_sliced_vbi_cap)
 #define VIDIOC_LOG_STATUS         _IO('V', 70)
 #define VIDIOC_G_EXT_CTRLS      _IOWR('V', 71, struct v4l2_ext_controls)