From 106b4a2a78b2a2f14885604891957b84bba502db Mon Sep 17 00:00:00 2001 From: Adrian Betschart Date: Fri, 11 Sep 2026 17:13:14 +0200 Subject: drm/amd/display: Try RGB before YCbCr 4:4:4 in stream validation amdgpu_dm_create_validate_stream_for_sink() walks encoding_order[] and uses the first encoding that validates. YCbCr 4:4:4 is listed before RGB, so an HDMI sink that advertises 4:4:4 gets YCbCr 4:4:4 whenever the "color format" property is left at AUTO, even though RGB fits the same link. That contradicts the documented AUTO behaviour for HDMI in enum drm_connector_color_format (RGB, falling back to YCbCr 4:2:0 only when the bandwidth is not available or the mode is 4:2:0-only), which the amdgpu implementation of the property also describes. It also leaves the "Broadcast RGB" property without effect on such sinks, since the quantization range it selects only applies to RGB output. Try RGB first. The mask still holds every encoding the sink supports, so a mode that cannot carry RGB falls back exactly as before. For reference, v7.2 picked RGB here unless YCbCr 4:4:4 was forced through debugfs, while earlier kernels picked YCbCr 4:4:4 for any HDMI sink that advertised it. Fixes: 0b0ff65d3ca1 ("drm/amd/display: Refactor stream validation") Suggested-by: Adolfo Rodrigues Assisted-by: Claude Code:claude-fable-5-1 Signed-off-by: Adrian Betschart Reviewed-by: Fangzhi Zuo Tested-by: Adolfo Rodrigues Tested-by: Daniel Wheeler Signed-off-by: Alex Deucher (cherry picked from commit 7de432bc753133764dc40d37f9388da56de251e7) --- samples/livepatch/livepatch-shadow-fix1.c | 173 ++++++++++++++++++++++++++++++ 1 file changed, 173 insertions(+) create mode 100644 samples/livepatch/livepatch-shadow-fix1.c (limited to 'samples/livepatch/livepatch-shadow-fix1.c') diff --git a/samples/livepatch/livepatch-shadow-fix1.c b/samples/livepatch/livepatch-shadow-fix1.c new file mode 100644 index 000000000..cbf68ca40 --- /dev/null +++ b/samples/livepatch/livepatch-shadow-fix1.c @@ -0,0 +1,173 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (C) 2017 Joe Lawrence + */ + +/* + * livepatch-shadow-fix1.c - Shadow variables, livepatch demo + * + * Purpose + * ------- + * + * Fixes the memory leak introduced in livepatch-shadow-mod through the + * use of a shadow variable. This fix demonstrates the "extending" of + * short-lived data structures by patching its allocation and release + * functions. + * + * + * Usage + * ----- + * + * This module is not intended to be standalone. See the "Usage" + * section of livepatch-shadow-mod.c. + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include +#include +#include +#include + +/* Shadow variable enums */ +#define SV_LEAK 1 + +/* Allocate new dummies every second */ +#define ALLOC_PERIOD 1 +/* Check for expired dummies after a few new ones have been allocated */ +#define CLEANUP_PERIOD (3 * ALLOC_PERIOD) +/* Dummies expire after a few cleanup instances */ +#define EXPIRE_PERIOD (4 * CLEANUP_PERIOD) + +struct dummy { + struct list_head list; + unsigned long jiffies_expire; +}; + +/* + * The constructor makes more sense together with klp_shadow_get_or_alloc(). + * In this example, it would be safe to assign the pointer also to the shadow + * variable returned by klp_shadow_alloc(). But we wanted to show the more + * complicated use of the API. + */ +static int shadow_leak_ctor(void *obj, void *shadow_data, void *ctor_data) +{ + int **shadow_leak = shadow_data; + int **leak = ctor_data; + + if (!ctor_data) + return -EINVAL; + + *shadow_leak = *leak; + return 0; +} + +static struct dummy *livepatch_fix1_dummy_alloc(void) +{ + struct dummy *d; + int *leak; + int **shadow_leak; + + d = kzalloc(sizeof(*d), GFP_KERNEL); + if (!d) + return NULL; + + d->jiffies_expire = jiffies + secs_to_jiffies(EXPIRE_PERIOD); + + /* + * Patch: save the extra memory location into a SV_LEAK shadow + * variable. A patched dummy_free routine can later fetch this + * pointer to handle resource release. + */ + leak = kzalloc(sizeof(*leak), GFP_KERNEL); + if (!leak) + goto err_leak; + + shadow_leak = klp_shadow_alloc(d, SV_LEAK, sizeof(leak), GFP_KERNEL, + shadow_leak_ctor, &leak); + if (!shadow_leak) { + pr_err("%s: failed to allocate shadow variable for the leaking pointer: dummy @ %p, leak @ %p\n", + __func__, d, leak); + goto err_shadow; + } + + pr_info("%s: dummy @ %p, expires @ %lx\n", + __func__, d, d->jiffies_expire); + + return d; + +err_shadow: + kfree(leak); +err_leak: + kfree(d); + return NULL; +} + +static void livepatch_fix1_dummy_leak_dtor(void *obj, void *shadow_data) +{ + void *d = obj; + int **shadow_leak = shadow_data; + + pr_info("%s: dummy @ %p, prevented leak @ %p\n", + __func__, d, *shadow_leak); + kfree(*shadow_leak); +} + +static void livepatch_fix1_dummy_free(struct dummy *d) +{ + int **shadow_leak; + + /* + * Patch: fetch the saved SV_LEAK shadow variable, detach and + * free it. Note: handle cases where this shadow variable does + * not exist (ie, dummy structures allocated before this livepatch + * was loaded.) + */ + shadow_leak = klp_shadow_get(d, SV_LEAK); + if (shadow_leak) + klp_shadow_free(d, SV_LEAK, livepatch_fix1_dummy_leak_dtor); + else + pr_info("%s: dummy @ %p leaked!\n", __func__, d); + + kfree(d); +} + +static struct klp_func funcs[] = { + { + .old_name = "dummy_alloc", + .new_func = livepatch_fix1_dummy_alloc, + }, + { + .old_name = "dummy_free", + .new_func = livepatch_fix1_dummy_free, + }, { } +}; + +static struct klp_object objs[] = { + { + .name = "livepatch_shadow_mod", + .funcs = funcs, + }, { } +}; + +static struct klp_patch patch = { + .mod = THIS_MODULE, + .objs = objs, +}; + +static int livepatch_shadow_fix1_init(void) +{ + return klp_enable_patch(&patch); +} + +static void livepatch_shadow_fix1_exit(void) +{ + /* Cleanup any existing SV_LEAK shadow variables */ + klp_shadow_free_all(SV_LEAK, livepatch_fix1_dummy_leak_dtor); +} + +module_init(livepatch_shadow_fix1_init); +module_exit(livepatch_shadow_fix1_exit); +MODULE_DESCRIPTION("Live patching demo for shadow variables"); +MODULE_LICENSE("GPL"); +MODULE_INFO(livepatch, "Y"); -- cgit v1.3.1