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Date:   Mon, 10 Sep 2018 15:11:34 +0100
From:   Ayan Halder <ayan.halder@arm.com>
To:     Brian Starkey <brian.starkey@arm.com>,
        dri-devel@lists.freedesktop.org, daniel@fooishbar.org,
        airlied@linux.ie, gustavo@padovan.org,
        maarten.lankhorst@linux.intel.com, seanpaul@chromium.org,
        linux-kernel@vger.kernel.org, alexandru-cosmin.gheorghe@arm.com,
        liviu.dudau@arm.com, tfiga@chromium.org, hoegsberg@chromium.org
Cc:     nd@arm.com
Subject: Re: [RFC PATCH v2 1/3] drm/fourcc: Add 'bpp' field for formats with
 non-integer bytes-per-pixel
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On Fri, Aug 31, 2018 at 10:17:30AM +0200, Daniel Vetter wrote:
> On Thu, Aug 23, 2018 at 04:23:41PM +0100, Brian Starkey wrote:
> > Some formats have a non-integer number of bytes per pixel, which can't
> > be handled with the existing 'cpp' field in drm_format_info. To handle
> > these formats, add a 'bpp' field, which is only used if cpp[0] == 0.
> > 
> > This updates all the users of format->cpp in the core DRM code,
> > converting them to use a new function to get the bits-per-pixel for any
> > format.
> > 
> > It's assumed that drivers will use the 'bpp' field when they add support
> > for pixel formats with non-integer bytes-per-pixel.
> > 
> > Signed-off-by: Brian Starkey <brian.starkey@arm.com>
> 
> I assume you still require that stuff is eventually aligned to bytes? In
> that case, can we subsume this into the tile work Alex is doing? It's
> essentially just another special case of having storage-size units
> measured in bytes which span more than 1x1 pixel. And I kinda don't want a
> metric pile of special cases here in the format code, because that just
> means every driver handles a different subset, with different bugs.
> -Daniel
> 
> > ---
> >  drivers/gpu/drm/drm_fb_cma_helper.c          |  6 +++-
> >  drivers/gpu/drm/drm_fb_helper.c              |  8 +++--
> >  drivers/gpu/drm/drm_fourcc.c                 | 50 ++++++++++++++++++++++++++++
> >  drivers/gpu/drm/drm_framebuffer.c            |  8 ++---
> >  drivers/gpu/drm/drm_gem_framebuffer_helper.c |  3 +-
> >  include/drm/drm_fourcc.h                     |  4 +++
> >  6 files changed, 70 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c b/drivers/gpu/drm/drm_fb_cma_helper.c
> > index 186d00adfb5f..e279d70d3e60 100644
> > --- a/drivers/gpu/drm/drm_fb_cma_helper.c
> > +++ b/drivers/gpu/drm/drm_fb_cma_helper.c
> > @@ -118,13 +118,17 @@ dma_addr_t drm_fb_cma_get_gem_addr(struct drm_framebuffer *fb,
> >  {
> >  	struct drm_gem_cma_object *obj;
> >  	dma_addr_t paddr;
> > +	u8 bpp = drm_format_info_plane_bpp(fb->format, plane);
> > +
> > +	/* This can't work for non-integer bytes-per-pixel */
> > +	WARN_ON(bpp % 8);
> >  
> >  	obj = drm_fb_cma_get_gem_obj(fb, plane);
> >  	if (!obj)
> >  		return 0;
> >  
> >  	paddr = obj->paddr + fb->offsets[plane];
> > -	paddr += fb->format->cpp[plane] * (state->src_x >> 16);
> > +	paddr += (bpp / 8) * (state->src_x >> 16);
> >  	paddr += fb->pitches[plane] * (state->src_y >> 16);
> >  
> >  	return paddr;
> > diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> > index 0646b108030b..ab369f250af4 100644
> > --- a/drivers/gpu/drm/drm_fb_helper.c
> > +++ b/drivers/gpu/drm/drm_fb_helper.c
> > @@ -1572,6 +1572,7 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
> >  	struct drm_fb_helper *fb_helper = info->par;
> >  	struct drm_framebuffer *fb = fb_helper->fb;
> >  	int depth;
> > +	u8 bpp = drm_format_info_plane_bpp(fb->format, 0);
> >  
> >  	if (var->pixclock != 0 || in_dbg_master())
> >  		return -EINVAL;
> > @@ -1580,14 +1581,14 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
> >  	 * Changes struct fb_var_screeninfo are currently not pushed back
> >  	 * to KMS, hence fail if different settings are requested.
> >  	 */
> > -	if (var->bits_per_pixel != fb->format->cpp[0] * 8 ||
> > +	if (var->bits_per_pixel != bpp ||
> >  	    var->xres > fb->width || var->yres > fb->height ||
> >  	    var->xres_virtual > fb->width || var->yres_virtual > fb->height) {
> >  		DRM_DEBUG("fb requested width/height/bpp can't fit in current fb "
> >  			  "request %dx%d-%d (virtual %dx%d) > %dx%d-%d\n",
> >  			  var->xres, var->yres, var->bits_per_pixel,
> >  			  var->xres_virtual, var->yres_virtual,
> > -			  fb->width, fb->height, fb->format->cpp[0] * 8);
> > +			  fb->width, fb->height, bpp);
> >  		return -EINVAL;
> >  	}
> >  
> > @@ -1949,11 +1950,12 @@ void drm_fb_helper_fill_var(struct fb_info *info, struct drm_fb_helper *fb_helpe
> >  			    uint32_t fb_width, uint32_t fb_height)
> >  {
> >  	struct drm_framebuffer *fb = fb_helper->fb;
> > +	u8 bpp = drm_format_info_plane_bpp(fb->format, 0);
> >  
> >  	info->pseudo_palette = fb_helper->pseudo_palette;
> >  	info->var.xres_virtual = fb->width;
> >  	info->var.yres_virtual = fb->height;
> > -	info->var.bits_per_pixel = fb->format->cpp[0] * 8;
> > +	info->var.bits_per_pixel = bpp;
> >  	info->var.accel_flags = FB_ACCELF_TEXT;
> >  	info->var.xoffset = 0;
> >  	info->var.yoffset = 0;
> > diff --git a/drivers/gpu/drm/drm_fourcc.c b/drivers/gpu/drm/drm_fourcc.c
> > index 3b42c25bd58d..bb28919c32f3 100644
> > --- a/drivers/gpu/drm/drm_fourcc.c
> > +++ b/drivers/gpu/drm/drm_fourcc.c
> > @@ -272,10 +272,60 @@ int drm_format_plane_cpp(uint32_t format, int plane)
> >  	if (!info || plane >= info->num_planes)
> >  		return 0;
> >  
> > +	/*
> > +	 * Not valid for formats with non-integer cpp,
> > +	 * use drm_format{_info}_plane_bpp instead
> > +	 */
> > +	WARN_ON(!info->cpp[0]);
> > +
> >  	return info->cpp[plane];
> >  }
> >  EXPORT_SYMBOL(drm_format_plane_cpp);
> >  
> > +/**
> > + * drm_format_plane_bpp - determine the bits per pixel value
> > + * @format: pixel format (DRM_FORMAT_*)
> > + * @plane: plane index
> > + *
> > + * Returns:
> > + * The bits per pixel value for the specified plane.
> > + */
> > +int drm_format_plane_bpp(uint32_t format, int plane)
> > +{
> > +	const struct drm_format_info *info;
> > +
> > +	info = drm_format_info(format);
> > +	if (!info)
> > +		return 0;
> > +
> > +	return drm_format_info_plane_bpp(info, plane);
> > +}
> > +EXPORT_SYMBOL(drm_format_plane_bpp);
> > +
> > +/**
> > + * drm_format_info_plane_bpp - determine the bits per pixel value
> > + *
> > + * Convenience function which handles formats with both integer
> > + * and non-integer bytes-per-pixel.
> > + *
> > + * @format: pixel format info structure
> > + * @plane: plane index
> > + *
> > + * Returns:
> > + * The bits per pixel value for the specified plane.
> > + */
> > +int drm_format_info_plane_bpp(const struct drm_format_info *info, int plane)
> > +{
> > +	if (plane >= info->num_planes)
> > +		return 0;
> > +
> > +	if (info->cpp[0])
> > +		return info->cpp[plane] * 8;
> > +
> > +	return info->bpp[plane];
> > +}
> > +EXPORT_SYMBOL(drm_format_info_plane_bpp);
> > +
> >  /**
> >   * drm_format_horz_chroma_subsampling - get the horizontal chroma subsampling factor
> >   * @format: pixel format (DRM_FORMAT_*)
> > diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c
> > index 8c4d32adcc17..7e00360ff70d 100644
> > --- a/drivers/gpu/drm/drm_framebuffer.c
> > +++ b/drivers/gpu/drm/drm_framebuffer.c
> > @@ -185,20 +185,20 @@ static int framebuffer_check(struct drm_device *dev,
> >  	for (i = 0; i < info->num_planes; i++) {
> >  		unsigned int width = fb_plane_width(r->width, info, i);
> >  		unsigned int height = fb_plane_height(r->height, info, i);
> > -		unsigned int cpp = info->cpp[i];
> > +		unsigned int bpp = drm_format_info_plane_bpp(info, i);
> >  
> >  		if (!r->handles[i]) {
> >  			DRM_DEBUG_KMS("no buffer object handle for plane %d\n", i);
> >  			return -EINVAL;
> >  		}
> >  
> > -		if ((uint64_t) width * cpp > UINT_MAX)
> > +		if ((uint64_t) DIV_ROUND_UP(width * bpp, 8) > UINT_MAX)
> >  			return -ERANGE;
> >  
> >  		if ((uint64_t) height * r->pitches[i] + r->offsets[i] > UINT_MAX)
> >  			return -ERANGE;
> >  
> > -		if (r->pitches[i] < width * cpp) {
> > +		if ((uint64_t) r->pitches[i] * 8 < (uint64_t) width * bpp) {
> >  			DRM_DEBUG_KMS("bad pitch %u for plane %d\n", r->pitches[i], i);
> >  			return -EINVAL;
> >  		}
> > @@ -476,7 +476,7 @@ int drm_mode_getfb(struct drm_device *dev,
> >  	r->height = fb->height;
> >  	r->width = fb->width;
> >  	r->depth = fb->format->depth;
> > -	r->bpp = fb->format->cpp[0] * 8;
> > +	r->bpp = drm_format_info_plane_bpp(fb->format, 0);
> >  	r->pitch = fb->pitches[0];
> >  
> >  	/* GET_FB() is an unprivileged ioctl so we must not return a
> > diff --git a/drivers/gpu/drm/drm_gem_framebuffer_helper.c b/drivers/gpu/drm/drm_gem_framebuffer_helper.c
> > index acfbc0641a06..dfe224ccaeba 100644
> > --- a/drivers/gpu/drm/drm_gem_framebuffer_helper.c
> > +++ b/drivers/gpu/drm/drm_gem_framebuffer_helper.c
> > @@ -161,6 +161,7 @@ drm_gem_fb_create_with_funcs(struct drm_device *dev, struct drm_file *file,
> >  		unsigned int width = mode_cmd->width / (i ? info->hsub : 1);
> >  		unsigned int height = mode_cmd->height / (i ? info->vsub : 1);
> >  		unsigned int min_size;
> > +		u8 bpp = drm_format_info_plane_bpp(fb->format, i);
You might want to pass info here instead of fb->format because fb is
NULL. ie drm_format_info_plane_bpp(info, i);

> >  
> >  		objs[i] = drm_gem_object_lookup(file, mode_cmd->handles[i]);
> >  		if (!objs[i]) {
> > @@ -170,7 +171,7 @@ drm_gem_fb_create_with_funcs(struct drm_device *dev, struct drm_file *file,
> >  		}
> >  
> >  		min_size = (height - 1) * mode_cmd->pitches[i]
> > -			 + width * info->cpp[i]
> > +			 + DIV_ROUND_UP(width * bpp, 8)
> >  			 + mode_cmd->offsets[i];
> >  
> >  		if (objs[i]->size < min_size) {
> > diff --git a/include/drm/drm_fourcc.h b/include/drm/drm_fourcc.h
> > index 3e86408dac9f..d4af4dab1623 100644
> > --- a/include/drm/drm_fourcc.h
> > +++ b/include/drm/drm_fourcc.h
> > @@ -36,6 +36,7 @@ struct drm_mode_fb_cmd2;
> >   *	use in new code and set to 0 for new formats.
> >   * @num_planes: Number of color planes (1 to 3)
> >   * @cpp: Number of bytes per pixel (per plane)
> > + * @bpp: Number of bits per pixel (per plane), only valid if cpp[0] == 0.
> >   * @hsub: Horizontal chroma subsampling factor
> >   * @vsub: Vertical chroma subsampling factor
> >   * @has_alpha: Does the format embeds an alpha component?
> > @@ -45,6 +46,7 @@ struct drm_format_info {
> >  	u8 depth;
> >  	u8 num_planes;
> >  	u8 cpp[3];
> > +	u8 bpp[3];
> >  	u8 hsub;
> >  	u8 vsub;
> >  	bool has_alpha;
> > @@ -66,6 +68,8 @@ drm_get_format_info(struct drm_device *dev,
> >  uint32_t drm_mode_legacy_fb_format(uint32_t bpp, uint32_t depth);
> >  int drm_format_num_planes(uint32_t format);
> >  int drm_format_plane_cpp(uint32_t format, int plane);
> > +int drm_format_plane_bpp(uint32_t format, int plane);
> > +int drm_format_info_plane_bpp(const struct drm_format_info *format, int plane);
> >  int drm_format_horz_chroma_subsampling(uint32_t format);
> >  int drm_format_vert_chroma_subsampling(uint32_t format);
> >  int drm_format_plane_width(int width, uint32_t format, int plane);
> > -- 
> > 2.16.1
> > 
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
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