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drm/dsi: use stack buffer in mipi_dsi_dcs_write()

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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>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200505160329.2976059-1-emil.l.velikov@gmail.com
This commit is contained in:
Emil Velikov 2020-05-05 17:03:27 +01:00 committed by Sam Ravnborg
parent 8767c3fc28
commit e192fba23e
1 changed files with 10 additions and 10 deletions
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20
drivers/gpu/drm/drm_mipi_dsi.c
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@ -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;