c4cba44eee
When ddc-i2c-bus property is used, a NULL pointer dereference is reported: [ 31.041669] Unable to handle kernel NULL pointer dereference at virtual address 00000008 [ 31.041671] pgd = 4d3c16f6 [ 31.041673] [00000008] *pgd=00000000 [ 31.041678] Internal error: Oops: 5 [#1] SMP ARM [ 31.041711] Hardware name: Rockchip (Device Tree) [ 31.041718] PC is at i2c_transfer+0x8/0xe4 [ 31.041721] LR is at drm_scdc_read+0x54/0x84 [ 31.041723] pc : [<c073273c>] lr : [<c05926c4>] psr: 280f0013 [ 31.041725] sp : edffdad0 ip : 5ccb5511 fp : 00000058 [ 31.041727] r10: 00000780 r9 : edf91608 r8 : c11b0f48 [ 31.041728] r7 : 00000438 r6 : 00000000 r5 : 00000000 r4 : 00000000 [ 31.041730] r3 : edffdae7 r2 : 00000002 r1 : edffdaec r0 : 00000000 [ 31.041908] [<c073273c>] (i2c_transfer) from [<c05926c4>] (drm_scdc_read+0x54/0x84) [ 31.041913] [<c05926c4>] (drm_scdc_read) from [<c0592858>] (drm_scdc_set_scrambling+0x30/0xbc) [ 31.041919] [<c0592858>] (drm_scdc_set_scrambling) from [<c05cc0f4>] (dw_hdmi_update_power+0x1440/0x1610) [ 31.041926] [<c05cc0f4>] (dw_hdmi_update_power) from [<c05cc574>] (dw_hdmi_bridge_enable+0x2c/0x70) [ 31.041932] [<c05cc574>] (dw_hdmi_bridge_enable) from [<c05aed48>] (drm_bridge_enable+0x24/0x34) [ 31.041938] [<c05aed48>] (drm_bridge_enable) from [<c0591060>] (drm_atomic_helper_commit_modeset_enables+0x114/0x220) [ 31.041943] [<c0591060>] (drm_atomic_helper_commit_modeset_enables) from [<c05c3fe0>] (rockchip_atomic_helper_commit_tail_rpm+0x28/0x64) hdmi->i2c may not be set when ddc-i2c-bus property is used in device tree. Fix this by using hdmi->ddc as the i2c adapter when calling drm_scdc_*(). Also report that SCDC is not supported when there is no DDC bus. Fixes: 264fce6cc2c1 ("drm/bridge: dw-hdmi: Add SCDC and TMDS Scrambling support") Signed-off-by: Jonas Karlman <jonas@kwiboo.se> Reviewed-by: Heiko Stuebner <heiko@sntech.de> Reviewed-by: Neil Armstrong <narmstrong@baylibre.com> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Andrzej Hajda <a.hajda@samsung.com> Link: https://patchwork.freedesktop.org/patch/msgid/VE1PR03MB59031814B5BCAB2152923BDAAC210@VE1PR03MB5903.eurprd03.prod.outlook.com
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.