On Thu, Jun 9, 2022 at 6:29 PM Jean-Jacques Hiblot
<jjhiblot@xxxxxxxxxxxxxxx> wrote:
>
> Settings multiple LEDs in a row can be a slow operation because of the
> time required to acquire the bus and prepare the transfer.
> And, in most cases, it is not required that the operation is synchronous.
>
> Implementing the non-blocking brightness_set() for such cases.
> A work queue is used to perform the actual SPI transfer.
>
> The blocking method is still available in case someone needs to perform
> this operation synchronously (ie by calling led_set_brightness_sync()).
i.e.
> +#define BITS_PER_ATOMIC (sizeof(atomic_t) * 8)
We have BITS_PER_TYPE(). Use it directly in the code, no need for a
whole new macro.
...
> +static int xmit(struct tlc5925_leds_priv *priv)
> +{
> + int i;
> +
> + spin_lock(&priv->lock);
This can't be called during IRQ?
> + for (i = 0; i < priv->max_state / (sizeof(atomic_t) * 8) ; i++)
BITS_PER_TYPE() ?
> + priv->spi_buffer[i] = atomic_read(&priv->state[i]);
> + spin_unlock(&priv->lock);
> +
> + return spi_write(priv->spi, priv->spi_buffer, priv->max_num_leds / 8);
> +}
...
> +static void xmit_work(struct work_struct *ws)
> +{
> + struct tlc5925_leds_priv *priv =
> + container_of(ws, struct tlc5925_leds_priv, xmit_work);
One line?
Missed blank line here.
> + xmit(priv);
> +};
...
> if (brightness)
> - priv->state[index / 8] |= (1 << (index % 8));
> + atomic_or(1 << (index % BITS_PER_ATOMIC),
> + &priv->state[index / BITS_PER_ATOMIC]);
> else
> - priv->state[index / 8] &= ~(1 << (index % 8));
> - spin_unlock(&priv->lock);
> + atomic_and(~(1 << (index % BITS_PER_ATOMIC)),
> + &priv->state[index / BITS_PER_ATOMIC]);
The whole bunch looks like reinventing the bitmap / bitops.
Use unsigned long (or DECLARE_BITMAP() if it can be higher than 32)
for state and set_bit() / clear_bit() / assign_bit() that are atomic.
...
> + if (brightness)
> + atomic_or(1 << (index % BITS_PER_ATOMIC),
> + &priv->state[index / BITS_PER_ATOMIC]);
> + else
> + atomic_and(~(1 << (index % BITS_PER_ATOMIC)),
> + &priv->state[index / BITS_PER_ATOMIC]);
assign_bit()
...
> + // Allocate the buffer used to hold the state of each LED
> + priv->max_state = round_up(max_num_leds, BITS_PER_ATOMIC);
> + priv->state = devm_kzalloc(dev,
> + priv->max_state / 8,
> + GFP_KERNEL);
> if (!priv->state)
> return -ENOMEM;
devm_bitmap_zalloc() ?
...
> + // Allocate a second buffer for the communication on the SPI bus
> + priv->spi_buffer = devm_kzalloc(dev,
> + priv->max_state / 8,
> + GFP_KERNEL);
Not sure I understand the output, but perhaps here the BITS_TO_BYTES()
should be used.
--
With Best Regards,
Andy Shevchenko
