linux-kernel - Re: [PATCH] drm/rockchip: fix for mailbox read size

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Message-ID: <7088529.fTnRXqZmiP@phil>
Date:   Mon, 19 Nov 2018 15:18:33 +0100
From:   Heiko Stuebner <heiko@...ech.de>
To:     Damian Kos <dkos@...ence.com>
Cc:     Chris Zhong <zyw@...k-chips.com>, Sandy Huang <hjc@...k-chips.com>,
        David Airlie <airlied@...ux.ie>,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/rockchip: fix for mailbox read size

Am Dienstag, 6. November 2018, 16:37:05 CET schrieb Damian Kos:
> Some of the functions (like cdn_dp_dpcd_read, cdn_dp_get_edid_block)
> allow to read 64KiB, but the cdn_dp_mailbox_read_receive, that is
> used by them, can read only up to 255 bytes at once. Normally, it's
> not a big issue as DPCD or EDID reads won't (hopefully) exceed that
> value.
> The real issue here is the revocation list read during the HDCP
> authentication process. (problematic use case:
> https://chromium.googlesource.com/chromiumos/third_party/kernel/+/chromeos-4.4/drivers/gpu/drm/rockchip/cdn-dp-reg.c#1152)
> The list can reach 127*5+4 bytes (num devs * 5 bytes per ID/Bksv +
> 4 bytes of an additional info).
> In other words - CTSes with HDCP Repeater won't pass without this
> fix. Oh, and the driver will most likely stop working (best case
> scenario).
> 
> Signed-off-by: Damian Kos <dkos@...ence.com>

applied to drm-misc-next

Thanks
Heiko