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[124.218.195.161]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2952699c9fbsm14113245ad.82.2025.10.31.01.06.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 31 Oct 2025 01:06:33 -0700 (PDT) From: LiangCheng Wang Date: Fri, 31 Oct 2025 16:06:30 +0800 Subject: [PATCH] drm/tiny: pixpaper: Prevent inlining of send helpers to reduce stack usage Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20251031-fix_202510270858-v1-1-6b111d475ce2@gmail.com> X-B4-Tracking: v=1; b=H4sIAAVuBGkC/6tWKk4tykwtVrJSqFYqSi3LLM7MzwNyDHUUlJIzE vPSU3UzU4B8JSMDI1NDA2ND3bTMingIx8jcwMLUQtco1cTMxDjJwMDUxFQJqK2gKBWoBmxkdGx tLQBOGmBZYgAAAA== X-Change-ID: 20251031-fix_202510270858-2e4643b00545 To: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, kernel test robot , LiangCheng Wang X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=ed25519-sha256; t=1761897992; l=2818; i=zaq14760@gmail.com; h=from:subject:message-id; bh=UuG3+VCNBbYpzeZ0dxVY03iZi2WsaJI6aqGWnRdi9IE=; b=mK5+SYBvGWn62MR/m+GdIu/nNPFIfMwQ2E2Ch9x0cFaUiEx+6Qf7V8YKLzV6lC9dvp44QfwL4 MS+Nsbaq2KSA97KntzVW89WCREuwcThUpa6N6adNPMod4GcASuBpKkk X-Developer-Key: i=zaq14760@gmail.com; a=ed25519; pk=/x4391DbJ19fFQI7t33HWt3lsHfYPl2I2ax8C+Vxr+M= Clang reports that pixpaper_panel_hw_init() exceeds the 8 KB stack frame limit: drivers/gpu/drm/tiny/pixpaper.c:579:12: warning: stack frame size (20024) exceeds limit (8192) in 'pixpaper_panel_hw_init' This warning occurs because the compiler aggressively inlines pixpaper_send_cmd() and pixpaper_send_data() into pixpaper_panel_hw_init(), which inflates the estimated stack usage. Mark these two helper functions as 'noinline' to prevent inlining. This significantly reduces the reported stack usage without changing runtime behavior. Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202510270858.1GzE6iQg-lkp@int= el.com/ Fixes: c9e70639f591 ("drm: tiny: Add support for Mayqueen Pixpaper e-ink pa= nel") Signed-off-by: LiangCheng Wang --- When building with Clang and frame size warnings enabled (-Wframe-larger-than=3D8192), the compiler reports that pixpaper_panel_hw_init() consumes over 20 KB of stack space: drivers/gpu/drm/tiny/pixpaper.c:579:12: warning: stack frame size (20024) exceeds limit (8192) in 'pixpaper_panel_hw_init' This happens because Clang aggressively inlines pixpaper_send_cmd() and pixpaper_send_data() into pixpaper_panel_hw_init(), causing the calculated stack usage to balloon far beyond the warning threshold. The fix is straightforward: mark these two helper functions as 'noinline' to prevent inlining. This reduces the reported stack usage to within normal limits without changing runtime behavior. --- drivers/gpu/drm/tiny/pixpaper.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/tiny/pixpaper.c b/drivers/gpu/drm/tiny/pixpape= r.c index 32598fb2fee7fcdea3ea0696c2bf54404fcffa2e..70e3239adfd0f86f92551991872= 486380489fb9b 100644 --- a/drivers/gpu/drm/tiny/pixpaper.c +++ b/drivers/gpu/drm/tiny/pixpaper.c @@ -536,7 +536,7 @@ static void pixpaper_spi_sync(struct spi_device *spi, s= truct spi_message *msg, err->errno_code =3D ret; } =20 -static void pixpaper_send_cmd(struct pixpaper_panel *panel, u8 cmd, +static noinline void pixpaper_send_cmd(struct pixpaper_panel *panel, u8 cm= d, struct pixpaper_error_ctx *err) { if (err->errno_code) @@ -556,7 +556,7 @@ static void pixpaper_send_cmd(struct pixpaper_panel *pa= nel, u8 cmd, pixpaper_spi_sync(panel->spi, &msg, err); } =20 -static void pixpaper_send_data(struct pixpaper_panel *panel, u8 data, +static noinline void pixpaper_send_data(struct pixpaper_panel *panel, u8 d= ata, struct pixpaper_error_ctx *err) { if (err->errno_code) --- base-commit: d127176862a93c4b3216bda533d2bee170af5e71 change-id: 20251031-fix_202510270858-2e4643b00545 Best regards, --=20 LiangCheng Wang