drm/mediatek: Add missing IS_ERR check for ovl_adaptor platform devicegrafted

platform_device_register_data() can fail and return an ERR_PTR, but the
return value is used without checking, leading to an invalid pointer
being stored in ddp_comp[].dev and passed to component_match_add() and
mtk_ddp_comp_init(), which could result in a kernel crash.

Add an IS_ERR() check to jump to the error handling path on failure.

Fixes: 0d9eee9118b7 ("drm/mediatek: Add drm ovl_adaptor sub driver for MT8195")
Cc: stable@vger.kernel.org
Signed-off-by: Haojie Li <lihaojie@kylinos.cn>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Link: https://patchwork.kernel.org/project/linux-mediatek/patch/20260825100845.438893-1-lihaojie@kylinos.cn/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>

1 files changed, 74 insertions, 0 deletions

diff --git a/Documentation/driver-api/sm501.rst b/Documentation/driver-api/sm501.rst
new file mode 100644
index 000000000..882507453
--- /dev/null
+++ b/Documentation/driver-api/sm501.rst
@@ -0,0 +1,74 @@
+.. include:: <isonum.txt>
+
+============
+SM501 Driver
+============
+
+:Copyright: |copy| 2006, 2007 Simtec Electronics
+
+The Silicon Motion SM501 multimedia companion chip is a multifunction device
+which may provide numerous interfaces including USB host controller USB gadget,
+asynchronous serial ports, audio functions, and a dual display video interface.
+The device may be connected by PCI or local bus with varying functions enabled.
+
+Core
+----
+
+The core driver in drivers/mfd provides common services for the
+drivers which manage the specific hardware blocks. These services
+include locking for common registers, clock control and resource
+management.
+
+The core registers drivers for both PCI and generic bus based
+chips via the platform device and driver system.
+
+On detection of a device, the core initialises the chip (which may
+be specified by the platform data) and then exports the selected
+peripheral set as platform devices for the specific drivers.
+
+The core re-uses the platform device system as the platform device
+system provides enough features to support the drivers without the
+need to create a new bus-type and the associated code to go with it.
+
+
+Resources
+---------
+
+Each peripheral has a view of the device which is implicitly narrowed to
+the specific set of resources that peripheral requires in order to
+function correctly.
+
+The centralised memory allocation allows the driver to ensure that the
+maximum possible resource allocation can be made to the video subsystem
+as this is by-far the most resource-sensitive of the on-chip functions.
+
+The primary issue with memory allocation is that of moving the video
+buffers once a display mode is chosen. Indeed when a video mode change
+occurs the memory footprint of the video subsystem changes.
+
+Since video memory is difficult to move without changing the display
+(unless sufficient contiguous memory can be provided for the old and new
+modes simultaneously) the video driver fully utilises the memory area
+given to it by aligning fb0 to the start of the area and fb1 to the end
+of it. Any memory left over in the middle is used for the acceleration
+functions, which are transient and thus their location is less critical
+as it can be moved.
+
+
+Configuration
+-------------
+
+The platform device driver uses a set of platform data to pass
+configurations through to the core and the subsidiary drivers
+so that there can be support for more than one system carrying
+an SM501 built into a single kernel image.
+
+The PCI driver assumes that the PCI card behaves as per the Silicon
+Motion reference design.
+
+There is an errata (AB-5) affecting the selection of the
+of the M1XCLK and M1CLK frequencies. These two clocks
+must be sourced from the same PLL, although they can then
+be divided down individually. If this is not set, then SM501 may
+lock and hang the whole system. The driver will refuse to
+attach if the PLL selection is different.