In dw_hdmi_probe(), casting the bitwise complement of (HDMI_PHY_HPD |
HDMI_PHY_RX_SENSE) directly to u8 triggers a compiler warning
(-Wconstant-conversion).

Due to C integer promotion rules, the bitwise OR and bitwise NOT are
evaluated as 32-bit signed integers, producing 0xFFFFFF0D before being
cast down to u8.

Fix this by explicitly masking the inverted 32-bit result with 0xFF
to keep only the lower byte and prevent implicit upper-bit truncation.

Signed-off-by: Sean Chang <seanwascoding@gmail.com>
---
 drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
index 34c5f583e910..937d61c42b58 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
@@ -3353,7 +3353,7 @@ struct dw_hdmi *dw_hdmi_probe(struct platform_device *pdev,
 	hdmi->channels = 2;
 	hdmi->disabled = true;
 	hdmi->rxsense = true;
-	hdmi->phy_mask = (u8)~(HDMI_PHY_HPD | HDMI_PHY_RX_SENSE);
+	hdmi->phy_mask = ~(HDMI_PHY_HPD | HDMI_PHY_RX_SENSE) & 0xff;
 	hdmi->mc_clkdis = 0x7f;
 	hdmi->last_connector_result = connector_status_disconnected;
 
-- 
2.43.0

On Wed, 19 Aug 2026 23:12:16 +0800, Sean Chang wrote:
> In dw_hdmi_probe(), casting the bitwise complement of (HDMI_PHY_HPD |
> HDMI_PHY_RX_SENSE) directly to u8 triggers a compiler warning
> (-Wconstant-conversion).
> 
> Due to C integer promotion rules, the bitwise OR and bitwise NOT are
> evaluated as 32-bit signed integers, producing 0xFFFFFF0D before being
> cast down to u8.
> 
> [...]

Applied, thanks!

[1/1] drm: bridge: dw_hdmi: Fix constant truncation warning on phy_mask
      commit: cb6a133bc75bc4c5b25f7c278b6c74bf46a3d71b

Best regards,
-- 
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

On Wed Aug 19, 2026 at 5:12 PM CEST, Sean Chang wrote:
> In dw_hdmi_probe(), casting the bitwise complement of (HDMI_PHY_HPD |
> HDMI_PHY_RX_SENSE) directly to u8 triggers a compiler warning
> (-Wconstant-conversion).
>
> Due to C integer promotion rules, the bitwise OR and bitwise NOT are
> evaluated as 32-bit signed integers, producing 0xFFFFFF0D before being
> cast down to u8.
>
> Fix this by explicitly masking the inverted 32-bit result with 0xFF
> to keep only the lower byte and prevent implicit upper-bit truncation.
>
> Signed-off-by: Sean Chang <seanwascoding@gmail.com>

Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com