On Tue, Oct 6, 2020 at 8:41 AM Luka Kovacic <luka.kovacic@xxxxxxxxxx> wrote:
>
> On Wed, Sep 30, 2020 at 9:48 PM Pavel Machek <pavel@xxxxxx> wrote:
> >
> > Hi!
> >
> > > +static int iei_wt61p803_puzzle_led_brightness_set_blocking(struct led_classdev *cdev,
> > > + enum led_brightness brightness)
> > > +{
> > > + struct iei_wt61p803_puzzle_led *priv = cdev_to_iei_wt61p803_puzzle_led(cdev);
> > > + unsigned char *resp_buf = priv->response_buffer;
> > > + unsigned char led_power_cmd[5] = {
> > > + IEI_WT61P803_PUZZLE_CMD_HEADER_START,
> > > + IEI_WT61P803_PUZZLE_CMD_LED,
> > > + IEI_WT61P803_PUZZLE_CMD_LED_POWER,
> > > + (char)IEI_LED_OFF
> > > + };
> > > + size_t reply_size;
> > > +
> > > + mutex_lock(&priv->lock);
> > > + if (brightness == LED_OFF) {
> > > + led_power_cmd[3] = (char)IEI_LED_OFF;
> > > + priv->led_power_state = LED_OFF;
> > > + } else {
> > > + led_power_cmd[3] = (char)IEI_LED_ON;
> > > + priv->led_power_state = LED_ON;
> > > + }
> > > + mutex_unlock(&priv->lock);
> > > +
> > > + return iei_wt61p803_puzzle_write_command(priv->mcu, led_power_cmd,
> > > + sizeof(led_power_cmd), resp_buf, &reply_size);
> > > +}
> >
> > Is the mutex needed? If so, should it include the
> > iei_wt61p803_puzzle_write_command()? Does
> > iei_wt61p803_puzzle_write_command() have internal locking to prevent
> > two messages from being mingled?
> >
> > Best regards,
> > Pavel
> >
> > --
> > (english) http://www.livejournal.com/~pavelmachek
> > (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
>
> Hello Pavel,
>
> The mutex isn't needed and can be removed.
> The function iei_wt61p803_puzzle_write_command() already handles its own
> mutex locking, so a separate mutex isn't required.
>
> Does brightness_set_blocking only block a single caller (each caller separately)
> or does it block all callers until the previous caller is finished?
>
> Kind regards,
> Luka
Hello Pavel,
I've sent out a new patchset, but I kept the mutex in use.
It's used to make sure only one read or write request is done at once,
when writing
to the LED driver private structure.
I have also added this description to the struct comment.
Kind regards,
Luka
