On Monday, November 09, 2015 10:04:03 PM Jakub Kiciński wrote:
>
> Florian,
Jakub, thank you for your patience with me. Of course you are right. I was to
blind to see it, when I split my original change in two parts.
>
> if we apply both of your patches the flow will be like this:
>
> 1. txlen = sc16is7xx_port_read(port, SC16IS7XX_TXLVL_REG);
> 2. if (txlen > SC16IS7XX_FIFO_SIZE) {
> 3. dev_err(...);
> 4. txlen = 0;
Here we drop an impossible input value.
> 5. }
> 6. to_send = (to_send > txlen) ? txlen : to_send;
> 7. /* Prevent ... */
> 8. to_send = (to_send > SC16IS7XX_FIFO_SIZE) ?
> 9. SC16IS7XX_FIFO_SIZE : to_send;
And this was intended to prevent the overrun itself.
> If we replace '= 0' on line 4 with = SC16IS7XX_FIFO_SIZE, this
> code can be rewritten as:
>
> 1. txlen = sc16is7xx_port_read(port, SC16IS7XX_TXLVL_REG);
> 2. txlen = min(txlen, SC16IS7XX_FIFO_SIZE);
> 3. to_send = min(txlen, to_send);
> 4. to_send = min(to_send, SC16IS7XX_FIFO_SIZE);
>
> Can you see now why I claim that your first patch is unnecessary?
> It's enough to make sure txlen is not larger than FIFO, since to_send
> cannot be larger than txlen it will never be larger than FIFO as well.
Yes, I can see now, thank you and sorry for my blindness.
What do we do? Pick only 2/2?
Sorry for causing so much work,
Florian
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