Currently the function heap allocates when we have any payload. Where in
many case the payload is 1 byte - ouch.
>From casual observation, vast majority of the payloads are smaller than
8 bytes - so use a stack array tx[8] to avoid the senseless kmalloc and
kfree dance.
Cc: Jani Nikula <jani.nikula@xxxxxxxxx>
Cc: Thierry Reding <treding@xxxxxxxxxx>
Signed-off-by: Emil Velikov <emil.velikov@xxxxxxxxxxxxx>
---
drivers/gpu/drm/drm_mipi_dsi.c | 20 ++++++++++----------
1 file changed, 10 insertions(+), 10 deletions(-)
diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
index 55531895dde6..b96d5b4629d7 100644
--- a/drivers/gpu/drm/drm_mipi_dsi.c
+++ b/drivers/gpu/drm/drm_mipi_dsi.c
@@ -748,26 +748,26 @@ ssize_t mipi_dsi_dcs_write(struct mipi_dsi_device *dsi, u8 cmd,
{
ssize_t err;
size_t size;
+ u8 stack_tx[8];
u8 *tx;
- if (len > 0) {
- size = 1 + len;
-
+ size = 1 + len;
+ if (len > ARRAY_SIZE(stack_tx) - 1) {
tx = kmalloc(size, GFP_KERNEL);
if (!tx)
return -ENOMEM;
-
- /* concatenate the DCS command byte and the payload */
- tx[0] = cmd;
- memcpy(&tx[1], data, len);
} else {
- tx = &cmd;
- size = 1;
+ tx = stack_tx;
}
+ /* concatenate the DCS command byte and the payload */
+ tx[0] = cmd;
+ if (data)
+ memcpy(&tx[1], data, len);
+
err = mipi_dsi_dcs_write_buffer(dsi, tx, size);
- if (len > 0)
+ if (tx != stack_tx)
kfree(tx);
return err;
--
2.25.1
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