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RCPT_COUNT_SEVEN(0.00)[10]; ASN(0.00)[asn:32098, ipnet:2800::/6, country:US]; RCVD_VIA_SMTP_AUTH(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.com:url,imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns,suse.de:mid,suse.de:dkim,suse.de:email] X-Rspamd-Action: no action X-Spam-Flag: NO X-Spam-Score: -4.51 X-Spam-Level: X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Rspamd-Queue-Id: 000AA4D256 Hi Am 16.03.26 um 12:38 schrieb Jani Nikula: > On Mon, 16 Mar 2026, Thomas Zimmermann wrote: >> Hi Jammy >> >> Am 13.03.26 um 11:04 schrieb Jammy Huang: >>> DisplayPort supports edid at most 256 bytes. Thus, allow it to fetch >>> edid block 0 and 1. >>> >>> Signed-off-by: Jammy Huang >>> --- >>> ASPEED DisplayPort's EDID size can be 256 bytes at most. Thus, EDID >>> blocks fetched can be 0 and 1. >>> --- >>> drivers/gpu/drm/ast/ast_dp.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/drivers/gpu/drm/ast/ast_dp.c b/drivers/gpu/drm/ast/ast_dp.c >>> index 9d07dad358c..c938e1d6b1d 100644 >>> --- a/drivers/gpu/drm/ast/ast_dp.c >>> +++ b/drivers/gpu/drm/ast/ast_dp.c >>> @@ -88,7 +88,7 @@ static int ast_astdp_read_edid_block(void *data, u8 *buf, unsigned int block, si >>> int ret = 0; >>> unsigned int i; >>> >>> - if (block > 0) >>> + if (block > 1) >>> return -EIO; /* extension headers not supported */ >> But see the code at [1]. It clears the number of extensions to zero and >> updates the checksum accordingly. This is required to make the shortened >> EDID work with DRM. If you leave this as-is, it will still clear support >> for any extension in block 1. >> >> See the table 2.4 in the VESA EDID 1.4 standard for the semantics. For >> 1.3, if the number of blocks is >2, the first extensions is a 'block map >> of the extensions'. This is useless, as it's not a data extension in >> itself.  In 1.4, the block map is optional. That code should clear the >> EDID's number of extensions to 0 or 1, depending on whether there is a >> block map to be expected. > I think long-term the goal should be for the kernel to not modify the > EDID, at all. We only fix up the checksum to address the fact that we cannot read the extensions. I guess the kernel could be fixed to work correctly with the extensions missing, but what about user space? Exporting an EDID without the extensions blocks could cause problems with user-space programs. Best regards Thomas > > BR, > Jani. > > >> Best regards >> Thomas >> >> [1] >> https://elixir.bootlin.com/linux/v6.19.8/source/drivers/gpu/drm/ast/ast_dp.c#L157 >> >>> >>> /* >>> >>> --- >>> base-commit: 5ee8dbf54602dc340d6235b1d6aa17c0f283f48c >>> change-id: 20260313-upstream_ast_dp_edid-5fe6adf7ad36 >>> >>> Best regards, -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)