Thomas Zimmermann <tzimmermann@xxxxxxx> writes: > Hi > > Am 06.11.21 um 22:02 schrieb Sven Schnelle: >> Thomas Zimmermann <tzimmermann@xxxxxxx> writes: >> >>> Hi >>> >>> Am 01.11.21 um 09:54 schrieb Sven Schnelle: >>>> Hi Thomas, >>>> Thomas Zimmermann <tzimmermann@xxxxxxx> writes: >>>> Thanks, i wasn't aware as i normally don't do any graphics related >>>> development. I take a look at dri and port the driver, which is >>>> hopefully not too hard. >>> >>> Sounds good. >>> >>> The one big difference when converting is that DRM really wants >>> drivers to support 32-bit XRGB colors. It's not a DRM limitation per >>> se, but a requirement of today's userspace programs. AFAICS your fbdev >>> driver uses a 256-color palette format. So the DRM driver would have >>> to convert >>> XRGB8888 to 8-bit RGB332 and install a corresponding palette. Don't >>> worry, it's easy. Take a look at the cirrus driver for a simple DRM >>> driver. [1] >> I have converted the driver, > > Cool! > >> but am using FORMAT_C8 because i haven't >> figured out yet how to switch the card to XRGB8888. That's still on the >> TODO list. > > Don't worry. As I outlined , you can still convert any image from > XRGB888 to RGB332 and display this instead. > >> One question about hw blitting: with the old fbdev framework one >> could >> replace the fb_imageblit function. For normal console text, this >> function gets called with a monochrome bitmap, and an fg/bg color value. >> This makes it easy to use HW accelerated blitting for text. In the >> gpu/drm drivers i think i found only one driver (nouveau) doing this and >> that was via the drm fbdev layer. >> Is that still the way to go, or is there a better way to do HW >> accelerated >> text blitting? > > Simply call drm_fbdev_generic_setup() after registering the > device. This should give you a console. Yes, that's what i have, and it works. The only thing that is odd (and i'm not sure whether that's a bug or not), is that fbset changes the resolution of the framebuffer, but doesn't reprogram the hardware to the new resolution. That means if i boot with 1920x1080 resolution, and do a fbset -a 640x480-60, only a small part of the screen is used now, but the physical resolution stays at 1920x1080. I first thought that's a bug in my driver, but my x86 Thinkpad X1 with nouveau behaves the same. > Don't bother about HW-accelerated blitting. From what I've heard, it > barely makes a difference nowadays. And our generic helpers have > plenty of features. Not using them to get a small benefit from HW > blitting isn't worth it. Not sure. With my first driver (the fbdev/fbcon one without drm), that made a big difference when scrolling or the whole screen was updated. I never measured it, but i would think it was a 1:10 ratio. Regards Sven
