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@intel.com Cc: Thierry Reding treding@nvidia.com Signed-off-by: Emil Velikov emil.velikov@collabora.com --- 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;