Hello Dong, On Tuesday 31 Jan 2017 15:49:34 DongCV wrote: > DearLaurent, > cc: Geert > > > Cfr. Laurent Pinchart's answer in the thread "Re: The failure summary > > > > report of GEN2 for linux stable v4.10-rc2": > > | I confirm your analysis. However, I think this isn't a new issue. Before > > | the aforementioned patch, running > > | > > | # fbset -xres 640 -yres 480 -laced 0 > > | # fbset -depth 16 -rgba 5,6,5,0 > > | > > | didn't produce any error, but didn't either resize the display to > > | 640x480 or changed the pixel format. With the patch applied, the > > | commands are rejected as they should be, as they wouldn't produce the > > | expected results. The new behaviour is thus in my opinion correct. > > > > http://www.mail-archive.com/linux-renesas-soc@xxxxxxxxxxxxxxx/msg10879.htm > > l > > I understood your opinion. > However,I wonder why the display size has changed when I implement the > following test procedure. > Could you explain it to me? > > * Changed the resolution. > - Perform the following command: > # bmap / dev / fb0 hdmi.bmp (Initial default size is 1024x768. Please > have look at 1024x768.jpg image) > # fbset -xres 640 -yres 480 -laced 0 > # bmap / dev / fb0 hdmi.bmp > > I saw the screen size has changed after running the following command. > "#fbset -xres -laced 0 480 640 -yres"(Please have look at 640x480.jpg image) > but I run the following command again > "#bmap / dev / fb0 hdmi.bmp", the image size did not change. > > Implement similarly with the 800x600 resolution. (Please have look at > 800x600.jpg image) That's because the screen resolution has not changed. Only the size reported to the fbdev emulation layer is updated, the screen resolution and framebuffer stay the same. This is exactly why changing the resolution through the fbdev device has been disabled recently, it just didn't work. This is a feature that will never be supported and should thus not be used. The purpose of the fbdev compatibility layer is to enable the framebuffer kernel console on top of a DRM/KMS device. The userspace API is available for applications to use, but they should not expect the full feature set of fbdev. Applications should be migrated to DRM/KMS. > * Changed the pixel format. > - Perform the following command: > # fbset -depth 16 -rgba 5,6,5,0 > # bmap /dev/fb0 hdmi.bmp > > (Please have look at pixel_16bit.jpg image) > > # fbset -depth 32 -rgba 5,6,5,0 > # bmap /dev/fb0 hdmi.bmp > > (Please have look at pixel_32bit.jpg image) > > I realize that 16bit set image differs from 32bit set image. > > Please have a look at the attached image for detail. This isn't supported for the same reason as above. -- Regards, Laurent Pinchart
