From e192fba23ef5ed1439fe699d808c480ca969b0ed Mon Sep 17 00:00:00 2001 From: Emil Velikov Date: Tue, 5 May 2020 17:03:27 +0100 Subject: [PATCH] drm/dsi: use stack buffer in mipi_dsi_dcs_write() 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 Cc: Thierry Reding Signed-off-by: Emil Velikov Reviewed-by: Thierry Reding Signed-off-by: Sam Ravnborg Link: https://patchwork.freedesktop.org/patch/msgid/20200505160329.2976059-1-emil.l.velikov@gmail.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; -- 2.11.0