Re: [PATCH v3 1/5] drm: move native byte order quirk to new drm_mode_legacy_fb_format2 function

[Daniel Vetter]

On Wed, Sep 19, 2018 at 01:12:48PM +0200, Gerd Hoffmann wrote:
> Turns out we need the pixel format fixup not only for the addfb ioctl,
> but also for fbdev emulation code.
> 
> Ideally we would place it in drm_mode_legacy_fb_format().  That would
> create alot of churn though, and most drivers don't care because they
> never ever run on a big endian platform.  So add a new
> drm_mode_legacy_fb_format2() function instead.
> 
> Signed-off-by: Gerd Hoffmann <kraxel@xxxxxxxxxx>
> ---
>  include/drm/drm_fourcc.h          |  2 ++
>  drivers/gpu/drm/drm_fourcc.c      | 28 ++++++++++++++++++++++++++++
>  drivers/gpu/drm/drm_framebuffer.c | 15 +++------------
>  3 files changed, 33 insertions(+), 12 deletions(-)
> 
> diff --git a/include/drm/drm_fourcc.h b/include/drm/drm_fourcc.h
> index fac831c401..4b82bb6576 100644
> --- a/include/drm/drm_fourcc.h
> +++ b/include/drm/drm_fourcc.h
> @@ -88,6 +88,8 @@ const struct drm_format_info *
>  drm_get_format_info(struct drm_device *dev,
>  		    const struct drm_mode_fb_cmd2 *mode_cmd);
>  uint32_t drm_mode_legacy_fb_format(uint32_t bpp, uint32_t depth);
> +uint32_t drm_mode_legacy_fb_format2(uint32_t bpp, uint32_t depth,
> +				    bool native);
>  int drm_format_num_planes(uint32_t format);
>  int drm_format_plane_cpp(uint32_t format, int plane);
>  int drm_format_horz_chroma_subsampling(uint32_t format);
> diff --git a/drivers/gpu/drm/drm_fourcc.c b/drivers/gpu/drm/drm_fourcc.c
> index be1d6aaef6..1c1aaa8b23 100644
> --- a/drivers/gpu/drm/drm_fourcc.c
> +++ b/drivers/gpu/drm/drm_fourcc.c
> @@ -96,6 +96,34 @@ uint32_t drm_mode_legacy_fb_format(uint32_t bpp, uint32_t depth)
>  EXPORT_SYMBOL(drm_mode_legacy_fb_format);
>  
>  /**
> + * drm_mode_legacy_fb_format2 - compute drm fourcc code from legacy description
> + * @bpp: bits per pixels
> + * @depth: bit depth per pixel
> + * @native: use host native byte order
> + *
> + * Computes a drm fourcc pixel format code for the given @bpp/@depth values.
> + * Useful in fbdev emulation code, since that deals in those values.
> + */
> +uint32_t drm_mode_legacy_fb_format2(uint32_t bpp, uint32_t depth,
> +				    bool native)

A _2 function is a bit meh imo. What about legacy_fb_format_native()
instead, which unconditionally gives you the native format, and then
pulling the if (native) out?

Or slightly more future proof (given that we have the nouveau hack too):

drm_device_legacy_fb_format(drm_device *dev, bpp, depth);

to make it clear that this is the device-specific conversion function.
-Daniel

> +{
> +	uint32_t fmt = drm_mode_legacy_fb_format(bpp, depth);
> +
> +	if (native) {
> +		if (fmt == DRM_FORMAT_XRGB8888)
> +			fmt = DRM_FORMAT_HOST_XRGB8888;
> +		if (fmt == DRM_FORMAT_ARGB8888)
> +			fmt = DRM_FORMAT_HOST_ARGB8888;
> +		if (fmt == DRM_FORMAT_RGB565)
> +			fmt = DRM_FORMAT_HOST_RGB565;
> +		if (fmt == DRM_FORMAT_XRGB1555)
> +			fmt = DRM_FORMAT_HOST_XRGB1555;
> +	}
> +	return fmt;
> +}
> +EXPORT_SYMBOL(drm_mode_legacy_fb_format2);
> +
> +/**
>   * drm_get_format_name - fill a string with a drm fourcc format's name
>   * @format: format to compute name of
>   * @buf: caller-supplied buffer
> diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c
> index 1ee3d6b442..f72e3dffc7 100644
> --- a/drivers/gpu/drm/drm_framebuffer.c
> +++ b/drivers/gpu/drm/drm_framebuffer.c
> @@ -111,12 +111,14 @@ int drm_mode_addfb(struct drm_device *dev, struct drm_mode_fb_cmd *or,
>  		   struct drm_file *file_priv)
>  {
>  	struct drm_mode_fb_cmd2 r = {};
> +	bool native = dev->mode_config.quirk_addfb_prefer_host_byte_order;
>  	int ret;
>  
>  	if (!drm_core_check_feature(dev, DRIVER_MODESET))
>  		return -EOPNOTSUPP;
>  
> -	r.pixel_format = drm_mode_legacy_fb_format(or->bpp, or->depth);
> +	r.pixel_format = drm_mode_legacy_fb_format2(or->bpp, or->depth,
> +						    native);
>  	if (r.pixel_format == DRM_FORMAT_INVALID) {
>  		DRM_DEBUG("bad {bpp:%d, depth:%d}\n", or->bpp, or->depth);
>  		return -EINVAL;
> @@ -133,17 +135,6 @@ int drm_mode_addfb(struct drm_device *dev, struct drm_mode_fb_cmd *or,
>  	    r.pixel_format == DRM_FORMAT_XRGB2101010)
>  		r.pixel_format = DRM_FORMAT_XBGR2101010;
>  
> -	if (dev->mode_config.quirk_addfb_prefer_host_byte_order) {
> -		if (r.pixel_format == DRM_FORMAT_XRGB8888)
> -			r.pixel_format = DRM_FORMAT_HOST_XRGB8888;
> -		if (r.pixel_format == DRM_FORMAT_ARGB8888)
> -			r.pixel_format = DRM_FORMAT_HOST_ARGB8888;
> -		if (r.pixel_format == DRM_FORMAT_RGB565)
> -			r.pixel_format = DRM_FORMAT_HOST_RGB565;
> -		if (r.pixel_format == DRM_FORMAT_XRGB1555)
> -			r.pixel_format = DRM_FORMAT_HOST_XRGB1555;
> -	}
> -
>  	ret = drm_mode_addfb2(dev, &r, file_priv);
>  	if (ret)
>  		return ret;
> -- 
> 2.9.3
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch