This is a note to let you know that I've just added the patch titled
firmware: coreboot: framebuffer: Ignore reserved pixel color bits
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
firmware-coreboot-framebuffer-ignore-reserved-pixel-color-bits.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From e6acaf25cba14661211bb72181c35dd13b24f5b3 Mon Sep 17 00:00:00 2001
From: Alper Nebi Yasak <alpernebiyasak@xxxxxxxxx>
Date: Sun, 22 Jan 2023 22:04:31 +0300
Subject: firmware: coreboot: framebuffer: Ignore reserved pixel color bits
From: Alper Nebi Yasak <alpernebiyasak@xxxxxxxxx>
commit e6acaf25cba14661211bb72181c35dd13b24f5b3 upstream.
The coreboot framebuffer doesn't support transparency, its 'reserved'
bit field is merely padding for byte/word alignment of pixel colors [1].
When trying to match the framebuffer to a simplefb format, the kernel
driver unnecessarily requires the format's transparency bit field to
exactly match this padding, even if the former is zero-width.
Due to a coreboot bug [2] (fixed upstream), some boards misreport the
reserved field's size as equal to its position (0x18 for both on a
'Lick' Chromebook), and the driver fails to probe where it would have
otherwise worked fine with e.g. the a8r8g8b8 or x8r8g8b8 formats.
Remove the transparency comparison with reserved bits. When the
bits-per-pixel and other color components match, transparency will
already be in a subset of the reserved field. Not forcing it to match
reserved bits allows the driver to work on the boards which misreport
the reserved field. It also enables using simplefb formats that don't
have transparency bits, although this doesn't currently happen due to
format support and ordering in linux/platform_data/simplefb.h.
[1] https://review.coreboot.org/plugins/gitiles/coreboot/+/4.19/src/commonlib/include/commonlib/coreboot_tables.h#255
[2] https://review.coreboot.org/plugins/gitiles/coreboot/+/4.13/src/drivers/intel/fsp2_0/graphics.c#82
Signed-off-by: Alper Nebi Yasak <alpernebiyasak@xxxxxxxxx>
Link: https://lore.kernel.org/r/20230122190433.195941-1-alpernebiyasak@xxxxxxxxx
Cc: Salvatore Bonaccorso <carnil@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/firmware/google/framebuffer-coreboot.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
--- a/drivers/firmware/google/framebuffer-coreboot.c
+++ b/drivers/firmware/google/framebuffer-coreboot.c
@@ -51,9 +51,7 @@ static int framebuffer_probe(struct core
fb->green_mask_pos == formats[i].green.offset &&
fb->green_mask_size == formats[i].green.length &&
fb->blue_mask_pos == formats[i].blue.offset &&
- fb->blue_mask_size == formats[i].blue.length &&
- fb->reserved_mask_pos == formats[i].transp.offset &&
- fb->reserved_mask_size == formats[i].transp.length)
+ fb->blue_mask_size == formats[i].blue.length)
pdata.format = formats[i].name;
}
if (!pdata.format)
Patches currently in stable-queue which might be from alpernebiyasak@xxxxxxxxx are
queue-4.19/firmware-coreboot-framebuffer-ignore-reserved-pixel-color-bits.patch
