From: Geert Uytterhoeven geert+renesas@glider.be
commit f30e27779d3031a092c2a177b7fb76adccc45241 upstream.
When userspace requests a video mode parameter value that is not supported, frame buffer device drivers should round it up to a supported value, if possible, instead of just rejecting it. This allows applications to quickly scan for supported video modes.
Currently this rule is not followed for the number of bits per pixel, causing e.g. "fbset -depth N" to fail, if N is smaller than the current number of bits per pixel.
Fix this by returning an error only if bits per pixel is too large, and setting it to the current value otherwise.
See also Documentation/fb/framebuffer.rst, Section 2 (Programmer's View of /dev/fb*").
Fixes: 865afb11949e5bf4 ("drm/fb-helper: reject any changes to the fbdev") Cc: stable@vger.kernel.org Signed-off-by: Geert Uytterhoeven geert+renesas@glider.be Signed-off-by: Daniel Vetter daniel.vetter@ffwll.ch Link: https://patchwork.freedesktop.org/patch/msgid/20191230132734.4538-1-geert+re... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/gpu/drm/drm_fb_helper.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
--- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -1320,7 +1320,7 @@ int drm_fb_helper_check_var(struct fb_va * 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 > fb->format->cpp[0] * 8 || 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 " @@ -1346,6 +1346,11 @@ int drm_fb_helper_check_var(struct fb_va }
/* + * Likewise, bits_per_pixel should be rounded up to a supported value. + */ + var->bits_per_pixel = fb->format->cpp[0] * 8; + + /* * drm fbdev emulation doesn't support changing the pixel format at all, * so reject all pixel format changing requests. */