On Mon, 13 May 2024, Hans de Goede wrote:
> On 5/13/24 2:12 PM, Ilpo Järvinen wrote:
> > On Mon, 13 May 2024, Hans de Goede wrote:
> >> On 5/13/24 10:34 AM, Ilpo Järvinen wrote:
> >>> On Sun, 12 May 2024, Hans de Goede wrote:
> >>>> +
> >>>> + dell_bl->resp_idx++;
> >>>> + if (dell_bl->resp_idx < dell_bl->resp_len)
> >>>> + continue;
> >>>> +
> >>>> + csum = dell_uart_checksum(dell_bl->resp, dell_bl->resp_len - 1);
> >>>> + if (dell_bl->resp[dell_bl->resp_len - 1] != csum) {
> >>>> + dev_err(dell_bl->dev, "Checksum mismatch got 0x%02x expected 0x%02x\n",
> >>>> + dell_bl->resp[dell_bl->resp_len - 1], csum);
> >>>> + dell_bl->status = -EIO;
> >>>> + goto wakeup;
> >>>> + }
> >>>
> >>> Why is the checksum calculation and check inside the loop??
> >>
> >> The loop iterates over received bytes, which may contain extra data
> >> after the response, the:
> >>
> >> dell_bl->resp_idx++;
> >> if (dell_bl->resp_idx < dell_bl->resp_len)
> >> continue;
> >>
> >> continues looping until we have received all the expected bytes. So here, past this
> >> check, we are are at the point where we have a complete response and then we verify it.
> >>
> >> And on successful verification wake-up any waiters.
> >
> > So effectively you want to terminate the loop on two conditions here:
> >
> > a) dell_bl->resp_idx == dell_bl->resp_len (complete frame)
> > a) if i == len (not yet received a full frame)
> >
> > Why not code those rather than the current goto & continue madness?
> >
> > Then, after the loop, you can test:
> >
> > if (dell_bl->resp_idx == dell_bl->resp_len) {
> > // calc checksum, etc.
> > }
> >
> > ?
>
> Ok, I've added the following change for v3:
>
> diff --git a/drivers/platform/x86/dell/dell-uart-backlight.c b/drivers/platform/x86/dell/dell-uart-backlight.c
> index bf5b12efcb19..66d8c6ddcb83 100644
> --- a/drivers/platform/x86/dell/dell-uart-backlight.c
> +++ b/drivers/platform/x86/dell/dell-uart-backlight.c
> @@ -87,6 +87,7 @@ static int dell_uart_bl_command(struct dell_uart_backlight *dell_bl,
> dell_bl->status = -EBUSY;
> dell_bl->resp = resp;
> dell_bl->resp_idx = 0;
> + dell_bl->resp_len = -1; /* Invalid / unset */
> dell_bl->resp_max_len = resp_max_len;
> dell_bl->pending_cmd = cmd[1];
>
> @@ -219,7 +219,7 @@ static size_t dell_uart_bl_receive(struct serdev_device *serdev, const u8 *data,
> return len;
> }
>
> - for (i = 0; i < len; i++) {
> + for (i = 0; i < len && dell_bl->resp_idx != dell_bl->resp_len; i++, dell_bl->resp_idx++) {
> dell_bl->resp[dell_bl->resp_idx] = data[i];
>
> switch (dell_bl->resp_idx) {
> @@ -228,46 +228,41 @@ static size_t dell_uart_bl_receive(struct serdev_device *serdev, const u8 *data,
> if (dell_bl->resp_len < MIN_RESP_LEN) {
> dev_err(dell_bl->dev, "Response length too small %d < %d\n",
> dell_bl->resp_len, MIN_RESP_LEN);
> - dell_bl->status = -EIO;
> - goto wakeup;
> + goto error;
> }
>
> if (dell_bl->resp_len > dell_bl->resp_max_len) {
> dev_err(dell_bl->dev, "Response length too big %d > %d\n",
> dell_bl->resp_len, dell_bl->resp_max_len);
> - dell_bl->status = -EIO;
> - goto wakeup;
> + goto error;
> }
> break;
> case RESP_CMD: /* CMD byte */
> if (dell_bl->resp[RESP_CMD] != dell_bl->pending_cmd) {
> dev_err(dell_bl->dev, "Response cmd 0x%02x != pending 0x%02x\n",
> dell_bl->resp[RESP_CMD], dell_bl->pending_cmd);
> - dell_bl->status = -EIO;
> - goto wakeup;
> + goto error;
> }
> break;
> }
> + }
>
> - dell_bl->resp_idx++;
> - if (dell_bl->resp_idx < dell_bl->resp_len)
> - continue;
> -
> + if (dell_bl->resp_idx == dell_bl->resp_len) {
> csum = dell_uart_checksum(dell_bl->resp, dell_bl->resp_len - 1);
> if (dell_bl->resp[dell_bl->resp_len - 1] != csum) {
> dev_err(dell_bl->dev, "Checksum mismatch got 0x%02x expected 0x%02x\n",
> dell_bl->resp[dell_bl->resp_len - 1], csum);
> - dell_bl->status = -EIO;
> - goto wakeup;
> + goto error;
> }
> -
> dell_bl->status = 0; /* Success */
> - goto wakeup;
> + wake_up(&dell_bl->wait_queue);
> + return i;
> }
>
> return len;
>
> -wakeup:
> +error:
> + dell_bl->status = -EIO;
> wake_up(&dell_bl->wait_queue);
> return i + 1;
> }
Thanks, this is way easier to follow.
--
i.
