Hi Am 15.05.23 um 20:04 schrieb Russell King (Oracle):
On Mon, May 15, 2023 at 07:55:44PM +0200, Sam Ravnborg wrote:Hi Thomas, On Mon, May 15, 2023 at 11:40:23AM +0200, Thomas Zimmermann wrote:Use the regular fbdev helpers for framebuffer I/O instead of DRM's helpers. Armada does not use damage handling, so DRM's fbdev helpers are mere wrappers around the fbdev code. By using fbdev helpers directly within each DRM fbdev emulation, we can eventually remove DRM's wrapper functions entirely. v2: * use FB_IO_HELPERS option Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx> Cc: Russell King <linux@xxxxxxxxxxxxxxx> --- drivers/gpu/drm/armada/Kconfig | 1 + drivers/gpu/drm/armada/armada_fbdev.c | 9 ++++----- 2 files changed, 5 insertions(+), 5 deletions(-) diff --git a/drivers/gpu/drm/armada/Kconfig b/drivers/gpu/drm/armada/Kconfig index f5c66d89ba99..5afade25e217 100644 --- a/drivers/gpu/drm/armada/Kconfig +++ b/drivers/gpu/drm/armada/Kconfig @@ -3,6 +3,7 @@ config DRM_ARMADA tristate "DRM support for Marvell Armada SoCs" depends on DRM && HAVE_CLK && ARM && MMU select DRM_KMS_HELPER + select FB_IO_HELPERS if DRM_FBDEV_EMULATION help Support the "LCD" controllers found on the Marvell Armada 510 devices. There are two controllers on the device, each controller diff --git a/drivers/gpu/drm/armada/armada_fbdev.c b/drivers/gpu/drm/armada/armada_fbdev.c index 0a5fd1aa86eb..6c3bbaf53569 100644 --- a/drivers/gpu/drm/armada/armada_fbdev.c +++ b/drivers/gpu/drm/armada/armada_fbdev.c @@ -5,6 +5,7 @@ */#include <linux/errno.h>+#include <linux/fb.h> #include <linux/kernel.h> #include <linux/module.h>@@ -34,11 +35,9 @@ static void armada_fbdev_fb_destroy(struct fb_info *info)static const struct fb_ops armada_fb_ops = { .owner = THIS_MODULE, DRM_FB_HELPER_DEFAULT_OPS, - .fb_read = drm_fb_helper_cfb_read, - .fb_write = drm_fb_helper_cfb_write,I had expected to see .fb_read = fb_io_read, But maybe this only used when using damage handling? Likewise for drm_fb_helper_cfb_write. ??- .fb_fillrect = drm_fb_helper_cfb_fillrect, - .fb_copyarea = drm_fb_helper_cfb_copyarea, - .fb_imageblit = drm_fb_helper_cfb_imageblit, + .fb_fillrect = cfb_fillrect, + .fb_copyarea = cfb_copyarea, + .fb_imageblit = cfb_imageblit,This part is as expected.Well, to me it looks like this has gone through an entire circular set of revisions: commit e8b70e4dd7b5dad7c2379de6e0851587bf86bfd6 Author: Archit Taneja <architt@xxxxxxxxxxxxxx> Date: Wed Jul 22 14:58:04 2015 +0530 drm/armada: Use new drm_fb_helper functions - .fb_fillrect = cfb_fillrect, - .fb_copyarea = cfb_copyarea, - .fb_imageblit = cfb_imageblit, + .fb_fillrect = drm_fb_helper_cfb_fillrect, + .fb_copyarea = drm_fb_helper_cfb_copyarea, + .fb_imageblit = drm_fb_helper_cfb_imageblit, commit 983780918c759fdbbf0bf033e701bbff75d2af23 Author: Thomas Zimmermann <tzimmermann@xxxxxxx> Date: Thu Nov 3 16:14:40 2022 +0100 drm/fb-helper: Perform all fbdev I/O with the same implementation + .fb_read = drm_fb_helper_cfb_read, + .fb_write = drm_fb_helper_cfb_write, and now effectively those two changes are being reverted, so we'd now be back to the pre-July 2015 state of affairs. As I believe the fbdev layer has been stable, this change merely reverts the driver back to what it once was.
Not quite. One long-standing problem has been that fbdev does not protect its public interfaces with CONFIG_FB. If fbdev had been disabled, DRM drivers could no longer be linked/loaded. DRM wrappers solved this. The issue has recently been fixed for all of DRM. DRM does not build it's fbdev emulation if CONFIG_FB has been disabled.
Another thing was that the original DRM wrappers might have been different from fbdev's I/O helpers in subtle ways. But now they are simple wrappers around their fbdev counterparts; plus the option of additional damage handling. But such damage handling is better implemented by the driver itself. The two cases that require it, i915 and fbdev-generic, are different enough that each should probably have it's own code.
Best regards Thomas
-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstrasse 146, 90461 Nuernberg, Germany GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB 36809 (AG Nuernberg)
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