Re: [PATCH 01/10] media: Introduce helpers to fill pixel format structs

[Ezequiel Garcia <ezequiel-ZGY8ohtN/8qB+jHODAdFcQ@public.gmane.org>]

On Wed, 2019-02-06 at 11:43 +0100, Hans Verkuil wrote:
> Hi Ezequiel,
> 
> A quick review below. This looks really useful, BTW.
> 
> On 2/5/19 9:24 PM, Ezequiel Garcia wrote:
> > Add two new API helpers, v4l2_fill_pixfmt and v4l2_fill_pixfmt_mp,
> > to be used by drivers to calculate plane sizes and bytes per lines.
> > 
> > Note that driver-specific paddig and alignment are not
> 
> paddig -> padding
> 
> > taken into account, and must be done by drivers using this API.
> > 
> > Signed-off-by: Ezequiel Garcia <ezequiel-ZGY8ohtN/8qB+jHODAdFcQ@public.gmane.org>
> > ---
> >  drivers/media/v4l2-core/Makefile      |   2 +-
> >  drivers/media/v4l2-core/v4l2-common.c |  71 +++++++++++++++++
> >  drivers/media/v4l2-core/v4l2-fourcc.c | 109 ++++++++++++++++++++++++++
> >  include/media/v4l2-common.h           |   5 ++
> >  include/media/v4l2-fourcc.h           |  53 +++++++++++++
> >  5 files changed, 239 insertions(+), 1 deletion(-)
> >  create mode 100644 drivers/media/v4l2-core/v4l2-fourcc.c
> >  create mode 100644 include/media/v4l2-fourcc.h
> > 
> > diff --git a/drivers/media/v4l2-core/Makefile b/drivers/media/v4l2-core/Makefile
> > index 9ee57e1efefe..bc23c3407c17 100644
> > --- a/drivers/media/v4l2-core/Makefile
> > +++ b/drivers/media/v4l2-core/Makefile
> > @@ -7,7 +7,7 @@ tuner-objs	:=	tuner-core.o
> >  
> >  videodev-objs	:=	v4l2-dev.o v4l2-ioctl.o v4l2-device.o v4l2-fh.o \
> >  			v4l2-event.o v4l2-ctrls.o v4l2-subdev.o v4l2-clk.o \
> > -			v4l2-async.o
> > +			v4l2-async.o v4l2-fourcc.o
> >  ifeq ($(CONFIG_COMPAT),y)
> >    videodev-objs += v4l2-compat-ioctl32.o
> >  endif
> > diff --git a/drivers/media/v4l2-core/v4l2-common.c b/drivers/media/v4l2-core/v4l2-common.c
> > index 50763fb42a1b..39d86a389cae 100644
> > --- a/drivers/media/v4l2-core/v4l2-common.c
> > +++ b/drivers/media/v4l2-core/v4l2-common.c
> > @@ -61,6 +61,7 @@
> >  #include <media/v4l2-common.h>
> >  #include <media/v4l2-device.h>
> >  #include <media/v4l2-ctrls.h>
> > +#include <media/v4l2-fourcc.h>
> 
> Either create a v4l2-fourcc.c source using this header, or move the
> contents of v4l2-fourcc.h to v4l2-common.h.
> 
> Creating a new header but not a new source is a bit weird.
> 

This patch adds v4l2-fourcc.c and v4l2-fourcc.h, containing
only the pixel format array and the fourcc name helper.

> >  
> >  #include <linux/videodev2.h>
> >  
> > @@ -455,3 +456,73 @@ int v4l2_s_parm_cap(struct video_device *vdev,
> >  	return ret;
> >  }
> >  EXPORT_SYMBOL_GPL(v4l2_s_parm_cap);
> > +
> > +void v4l2_fill_pixfmt_mp(struct v4l2_pix_format_mplane *pixfmt,
> > +			 int pixelformat, int width, int height)
> > +{
> > +	const struct v4l2_format_info *info;
> > +	struct v4l2_plane_pix_format *plane;
> > +	int i;
> > +
> > +	info = v4l2_format_info(pixelformat);
> > +	if (!info)
> > +		return;
> 
> You should return a bool or something to indicate whether or not
> the pixelformat was known.
> 

Got it.

> > +
> > +	pixfmt->width = width;
> > +	pixfmt->height = height;
> > +	pixfmt->pixelformat = pixelformat;
> > +
> > +	if (!info->multiplanar) {
> 
> It would make much more sense if multiplanar contained the number of
> planes to use (i.e. equal to pixfmt->num_planes).
> 
> See more about this below.
> 
> > +		pixfmt->num_planes = 1;
> > +		plane = &pixfmt->plane_fmt[0];
> > +		plane->bytesperline = width * info->cpp[0];
> > +		plane->sizeimage = 0;
> > +		for (i = 0; i < info->num_planes; i++) {
> > +			unsigned int hsub = (i == 0) ? 1 : info->hsub;
> > +			unsigned int vsub = (i == 0) ? 1 : info->vsub;
> > +
> > +			plane->sizeimage += info->cpp[i] *
> > +				DIV_ROUND_UP(width, hsub) *
> > +				DIV_ROUND_UP(height, vsub);
> > +		}
> > +	} else {
> > +		pixfmt->num_planes = info->num_planes;
> > +		for (i = 0; i < info->num_planes; i++) {
> > +			unsigned int hsub = (i == 0) ? 1 : info->hsub;
> > +			unsigned int vsub = (i == 0) ? 1 : info->vsub;
> > +
> > +			plane = &pixfmt->plane_fmt[i];
> > +			plane->bytesperline =
> > +				info->cpp[i] * DIV_ROUND_UP(width, hsub);
> > +			plane->sizeimage =
> > +				plane->bytesperline * DIV_ROUND_UP(height, vsub);
> > +		}
> > +	}
> > +}
> > +EXPORT_SYMBOL_GPL(v4l2_fill_pixfmt_mp);
> > +
> > +void v4l2_fill_pixfmt(struct v4l2_pix_format *pixfmt, int pixelformat, int width, int height)
> > +{
> > +	const struct v4l2_format_info *info;
> > +	int i;
> > +
> > +	info = v4l2_format_info(pixelformat);
> > +	if (!info)
> > +		return;
> 
> You have to check if pixelformat was a multiplanar format and reject it.
> 

OK.

> > +
> > +	pixfmt->width = width;
> > +	pixfmt->height = height;
> > +	pixfmt->pixelformat = pixelformat;
> > +	pixfmt->bytesperline = width * info->cpp[0];
> > +	pixfmt->sizeimage = 0;
> > +
> > +	for (i = 0; i < info->num_planes; i++) {
> > +		unsigned int hsub = (i == 0) ? 1 : info->hsub;
> > +		unsigned int vsub = (i == 0) ? 1 : info->vsub;
> > +
> > +		pixfmt->sizeimage += info->cpp[i] *
> > +			DIV_ROUND_UP(width, hsub) *
> > +			DIV_ROUND_UP(height, vsub);
> > +	}
> > +}
> > +EXPORT_SYMBOL_GPL(v4l2_fill_pixfmt);
> > diff --git a/drivers/media/v4l2-core/v4l2-fourcc.c b/drivers/media/v4l2-core/v4l2-fourcc.c
> > new file mode 100644
> > index 000000000000..982c0ffa1a66
> > --- /dev/null
> > +++ b/drivers/media/v4l2-core/v4l2-fourcc.c
> > @@ -0,0 +1,109 @@
> > +/*
> > + * Copyright (c) 2018 Collabora, Ltd.
> > + *
> > + * Based on drm-fourcc:
> > + * Copyright (c) 2016 Laurent Pinchart <laurent.pinchart-ryLnwIuWjnjg/C1BVhZhaw@public.gmane.org>
> > + *
> > + * Permission to use, copy, modify, distribute, and sell this software and its
> > + * documentation for any purpose is hereby granted without fee, provided that
> > + * the above copyright notice appear in all copies and that both that copyright
> > + * notice and this permission notice appear in supporting documentation, and
> > + * that the name of the copyright holders not be used in advertising or
> > + * publicity pertaining to distribution of the software without specific,
> > + * written prior permission.  The copyright holders make no representations
> > + * about the suitability of this software for any purpose.  It is provided "as
> > + * is" without express or implied warranty.
> > + *
> > + * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
> > + * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
> > + * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
> > + * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
> > + * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
> > + * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
> > + * OF THIS SOFTWARE.
> > + */
> > +
> > +#include <linux/ctype.h>
> > +#include <linux/videodev2.h>
> > +#include <media/v4l2-fourcc.h>
> > +
> > +static char printable_char(int c)
> > +{
> > +	return isascii(c) && isprint(c) ? c : '?';
> > +}
> > +
> > +const char *v4l2_get_format_name(uint32_t format)
> 
> This should be called v4l2_get_fourcc_name. The format name is what ENUMFMT returns.
> 

Got it.

> > +{
> > +	static char buf[4];
> > +
> > +	snprintf(buf, 4,
> > +		 "%c%c%c%c",
> > +		 printable_char(format & 0xff),
> > +		 printable_char((format >> 8) & 0xff),
> > +		 printable_char((format >> 16) & 0xff),
> > +		 printable_char((format >> 24) & 0x7f));
> 
> If bit 31 is set, then add a '-BE' suffix to indicate that this is a
> big endian variant of the same pixelformat with bit 31 set to 0.
> 
> See also v4l_fill_fmtdesc() in v4l2-ioctl.c.
> 

I omitted endianness and alpha because they weren't used
by V4L2, but let me add them to make the code generic
and support out-of-tree stuff.

> > +
> > +	return buf;
> > +}
> > +EXPORT_SYMBOL(v4l2_get_format_name);
> 
> I remember that Sakari tried to make a macro for this in a public header, but
> it was either rejected or fizzled out:
> 
> https://www.mail-archive.com/linux-media-u79uwXL29TY76Z2rM5mHXA@public.gmane.org/msg128702.html
> 

I see. This time we are adding the fourcc name helper to the private API,
which shouldn't cause too much debate. Adding Sakari to the loop.

> > +
> > +const struct v4l2_format_info *v4l2_format_info(u32 format)
> > +{
> > +	static const struct v4l2_format_info formats[] = {
> > +		/* RGB formats */
> > +		{ .format = V4L2_PIX_FMT_BGR24,		.num_planes = 1, .cpp = { 3, 0, 0 }, .hsub = 1, .vsub = 1 },
> > +		{ .format = V4L2_PIX_FMT_RGB24,		.num_planes = 1, .cpp = { 3, 0, 0 }, .hsub = 1, .vsub = 1 },
> > +		{ .format = V4L2_PIX_FMT_HSV24,		.num_planes = 1, .cpp = { 3, 0, 0 }, .hsub = 1, .vsub = 1 },
> > +		{ .format = V4L2_PIX_FMT_BGR32,		.num_planes = 1, .cpp = { 4, 0, 0 }, .hsub = 1, .vsub = 1 },
> > +		{ .format = V4L2_PIX_FMT_XBGR32,	.num_planes = 1, .cpp = { 4, 0, 0 }, .hsub = 1, .vsub = 1 },
> > +		{ .format = V4L2_PIX_FMT_RGB32,		.num_planes = 1, .cpp = { 4, 0, 0 }, .hsub = 1, .vsub = 1 },
> > +		{ .format = V4L2_PIX_FMT_XRGB32,	.num_planes = 1, .cpp = { 4, 0, 0 }, .hsub = 1, .vsub = 1 },
> > +		{ .format = V4L2_PIX_FMT_HSV32,		.num_planes = 1, .cpp = { 4, 0, 0 }, .hsub = 1, .vsub = 1 },
> > +		{ .format = V4L2_PIX_FMT_ARGB32,	.num_planes = 1, .cpp = { 4, 0, 0 }, .hsub = 1, .vsub = 1 },
> > +		{ .format = V4L2_PIX_FMT_ABGR32,	.num_planes = 1, .cpp = { 4, 0, 0 }, .hsub = 1, .vsub = 1 },
> > +		{ .format = V4L2_PIX_FMT_GREY,		.num_planes = 1, .cpp = { 1, 0, 0 }, .hsub = 1, .vsub = 1 },
> > +
> > +		/* YUV formats */
> > +		{ .format = V4L2_PIX_FMT_YUYV,		.num_planes = 1, .cpp = { 2, 0, 0 }, .hsub = 2, .vsub = 1 },
> > +		{ .format = V4L2_PIX_FMT_YVYU,		.num_planes = 1, .cpp = { 2, 0, 0 }, .hsub = 2, .vsub = 1 },
> > +		{ .format = V4L2_PIX_FMT_UYVY,		.num_planes = 1, .cpp = { 2, 0, 0 }, .hsub = 2, .vsub = 1 },
> > +		{ .format = V4L2_PIX_FMT_VYUY,		.num_planes = 1, .cpp = { 2, 0, 0 }, .hsub = 2, .vsub = 1 },
> > +
> > +		{ .format = V4L2_PIX_FMT_NV12,		.num_planes = 2, .cpp = { 1, 2, 0 }, .hsub = 2, .vsub = 2 },
> > +		{ .format = V4L2_PIX_FMT_NV21,		.num_planes = 2, .cpp = { 1, 2, 0 }, .hsub = 2, .vsub = 2 },
> > +		{ .format = V4L2_PIX_FMT_NV16,		.num_planes = 2, .cpp = { 1, 2, 0 }, .hsub = 2, .vsub = 1 },
> > +		{ .format = V4L2_PIX_FMT_NV61,		.num_planes = 2, .cpp = { 1, 2, 0 }, .hsub = 2, .vsub = 1 },
> > +		{ .format = V4L2_PIX_FMT_NV24,		.num_planes = 2, .cpp = { 1, 2, 0 }, .hsub = 1, .vsub = 1 },
> > +		{ .format = V4L2_PIX_FMT_NV42,		.num_planes = 2, .cpp = { 1, 2, 0 }, .hsub = 1, .vsub = 1 },
> > +
> > +		{ .format = V4L2_PIX_FMT_YUV410,	.num_planes = 3, .cpp = { 1, 1, 1 }, .hsub = 4, .vsub = 4 },
> > +		{ .format = V4L2_PIX_FMT_YVU410,	.num_planes = 3, .cpp = { 1, 1, 1 }, .hsub = 4, .vsub = 4 },
> > +		{ .format = V4L2_PIX_FMT_YUV411P,	.num_planes = 3, .cpp = { 1, 1, 1 }, .hsub = 4, .vsub = 1 },
> > +		{ .format = V4L2_PIX_FMT_YUV420,	.num_planes = 3, .cpp = { 1, 1, 1 }, .hsub = 2, .vsub = 2 },
> > +		{ .format = V4L2_PIX_FMT_YVU420,	.num_planes = 3, .cpp = { 1, 1, 1 }, .hsub = 2, .vsub = 2 },
> > +		{ .format = V4L2_PIX_FMT_YUV422P,	.num_planes = 3, .cpp = { 1, 1, 1 }, .hsub = 2, .vsub = 1 },
> > +
> > +		{ .format = V4L2_PIX_FMT_YUV420M,	.num_planes = 3, .cpp = { 1, 1, 1 }, .hsub = 2, .vsub = 2, .multiplanar = 1 },
> > +		{ .format = V4L2_PIX_FMT_YVU420M,	.num_planes = 3, .cpp = { 1, 1, 1 }, .hsub = 2, .vsub = 2, .multiplanar = 1 },
> > +		{ .format = V4L2_PIX_FMT_YUV422M,	.num_planes = 3, .cpp = { 1, 1, 1 }, .hsub = 2, .vsub = 1, .multiplanar = 1 },
> > +		{ .format = V4L2_PIX_FMT_YVU422M,	.num_planes = 3, .cpp = { 1, 1, 1 }, .hsub = 2, .vsub = 1, .multiplanar = 1 },
> > +		{ .format = V4L2_PIX_FMT_YUV444M,	.num_planes = 3, .cpp = { 1, 1, 1 }, .hsub = 1, .vsub = 1, .multiplanar = 1 },
> > +		{ .format = V4L2_PIX_FMT_YVU444M,	.num_planes = 3, .cpp = { 1, 1, 1 }, .hsub = 1, .vsub = 1, .multiplanar = 1 },
> > +
> > +		{ .format = V4L2_PIX_FMT_NV12M,		.num_planes = 2, .cpp = { 1, 2, 0 }, .hsub = 2, .vsub = 2, .multiplanar = 1 },
> > +		{ .format = V4L2_PIX_FMT_NV21M,		.num_planes = 2, .cpp = { 1, 2, 0 }, .hsub = 2, .vsub = 2, .multiplanar = 1 },
> > +		{ .format = V4L2_PIX_FMT_NV16M,		.num_planes = 2, .cpp = { 1, 2, 0 }, .hsub = 2, .vsub = 1, .multiplanar = 1 },
> > +		{ .format = V4L2_PIX_FMT_NV61M,		.num_planes = 2, .cpp = { 1, 2, 0 }, .hsub = 2, .vsub = 1, .multiplanar = 1 },
> > +
> > +	};
> > +	unsigned int i;
> > +
> > +	for (i = 0; i < ARRAY_SIZE(formats); ++i) {
> > +		if (formats[i].format == format)
> > +			return &formats[i];
> > +	}
> 
> No need for {}
> 

OK

> > +
> > +	pr_warn("Unsupported V4L 4CC format %s (%08x)\n", v4l2_get_format_name(format), format);
> 
> Make this a pr_dev or remove it altogether. I prefer the latter.
> 

Right. If the function returns an error condition, we can drop it.

> > +	return NULL;
> > +}
> > +EXPORT_SYMBOL(v4l2_format_info);
> > diff --git a/include/media/v4l2-common.h b/include/media/v4l2-common.h
> > index 0c511ed8ffb0..6461ce747d90 100644
> > --- a/include/media/v4l2-common.h
> > +++ b/include/media/v4l2-common.h
> > @@ -327,6 +327,11 @@ void v4l_bound_align_image(unsigned int *width, unsigned int wmin,
> >  			   unsigned int hmax, unsigned int halign,
> >  			   unsigned int salign);
> >  
> > +void v4l2_fill_pixfmt(struct v4l2_pix_format *pixfmt, int pixelformat,
> > +		      int width, int height);
> > +void v4l2_fill_pixfmt_mp(struct v4l2_pix_format_mplane *pixfmt, int pixelformat,
> > +			 int width, int height);
> > +
> >  /**
> >   * v4l2_find_nearest_size - Find the nearest size among a discrete
> >   *	set of resolutions contained in an array of a driver specific struct.
> > diff --git a/include/media/v4l2-fourcc.h b/include/media/v4l2-fourcc.h
> > new file mode 100644
> > index 000000000000..3d24f442aaf5
> > --- /dev/null
> > +++ b/include/media/v4l2-fourcc.h
> > @@ -0,0 +1,53 @@
> > +/*
> > + * Copyright (c) 2018 Collabora, Ltd.
> > + *
> > + * Based on drm-fourcc:
> > + * Copyright (c) 2016 Laurent Pinchart <laurent.pinchart-ryLnwIuWjnjg/C1BVhZhaw@public.gmane.org>
> > + *
> > + * Permission to use, copy, modify, distribute, and sell this software and its
> > + * documentation for any purpose is hereby granted without fee, provided that
> > + * the above copyright notice appear in all copies and that both that copyright
> > + * notice and this permission notice appear in supporting documentation, and
> > + * that the name of the copyright holders not be used in advertising or
> > + * publicity pertaining to distribution of the software without specific,
> > + * written prior permission.  The copyright holders make no representations
> > + * about the suitability of this software for any purpose.  It is provided "as
> > + * is" without express or implied warranty.
> > + *
> > + * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
> > + * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
> > + * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
> > + * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
> > + * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
> > + * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
> > + * OF THIS SOFTWARE.
> 
> Should be an SPDX ID.
> 
> > + */
> > +#ifndef __V4L2_FOURCC_H__
> > +#define __V4L2_FOURCC_H__
> > +
> > +#include <linux/types.h>
> > +
> > +/**
> > + * struct v4l2_format_info - information about a V4L2 format
> > + * @format: 4CC format identifier (V4L2_PIX_FMT_*)
> > + * @header_size: Size of header, optional and used by compressed formats
> > + * @num_planes: Number of planes (1 to 3)
> 
> This is actually 1-4 since there may be an alpha channel as well. Not that we have
> such formats since the only formats with an alpha channel are interleaved formats,
> but it is possible.
> 
> So this value is 2 for both NV12 and NV12M.
> 
> > + * @cpp: Number of bytes per pixel (per plane)
> 
> cpp? Shouldn't that be bpp?
> 
> Note that this can differ per plane (see e.g. NV24).
> 

Yes, the comment should specify that it's an array of bytes per pixel.

And the naming follows drm-fourcc. cpp stands for char-per-pixel.
It may be confusing but at the same time, I really like to have
consistent naming across the board (think for instance in
the DMA coherent/consistent aliases).

Also, note that drm-fourcc deprecates cpp, to support tile formats.
Hopefully we don't need that here?
 
> > + * @hsub: Horizontal chroma subsampling factor
> > + * @vsub: Vertical chroma subsampling factor
> 
> A bit too cryptic IMHO. I would prefer hdiv or hsubsampling. 'hsub' suggests
> subtraction :-)
> 

Ditto, this name follows drm-fourcc. I'm fine either way.

> > + * @multiplanar: Is it a multiplanar variant format? (e.g. NV12M)
> 
> This should, I think, be renamed to num_non_contig_planes to indicate how many
> non-contiguous planes there are in the format.
> 
> So this value is 1 for NV12 and 2 for NV12M. For V4L2_PIX_FMT_YUV444M it is 3.
> 
> You can stick this value directly into pixfmt_mp->num_planes.
> 

Fine by me, but I have to admit I don't see the value of adding the
number of non-contiguous planes. For multiplanar non-contiguous formats
the number of planes is equal to the number of planes.

Although maybe it will be clear this way for readers?

> As an aside: perhaps we should start calling the 'multiplanar API' the
> 'multiple non-contiguous planes API', at least in the documentation. It's the
> first time that I found a description that actually covers the real meaning.
> 

Yes, indeed. In fact, my first version of this code had something like
"is_noncontiguous" instead of the "multiplanar" field.

> > + */
> > +struct v4l2_format_info {
> > +	u32 format;
> > +	u32 header_size;
> > +	u8 num_planes;
> > +	u8 cpp[3];
> > +	u8 hsub;
> > +	u8 vsub;
> > +	u8 multiplanar;
> > +};
> > +
> > +const struct v4l2_format_info *v4l2_format_info(u32 format);
> > +const char *v4l2_get_format_name(u32 format);
> > +
> > +#endif
> > 
> 

Thanks a lot for the thorough review!

> Regards,
> 
> 	Hans