Re: [PATCH 1/3] drm/dsi: use stack buffer in mipi_dsi_dcs_write()

On Thu, May 28, 2020 at 05:47:41PM +0100, Emil Velikov wrote:

On Tue, 5 May 2020 at 17:05, Emil Velikov emil.l.velikov@gmail.com wrote:

...

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;
  

--

Thierry, others - humble ping. Can you check through the series?

I don't see patch 2 of this series anywhere? Did it fall victim to some filter?

Thierry