Hi Hubert,
2011/6/24 Hubert Feurstein <h.feurstein@xxxxxxxxx>
Hi Franck,
2011/6/23 Franck JULLIEN <franck.jullien@xxxxxxxxx>:
> Hello, I have a question regarding the SPI spi_write_then_read function.[snip]
>
>> +int spi_write_then_read(struct spi_device *spi,Because this function will *not* write to the data of txbuf. With the
>> + const void *txbuf, unsigned n_tx,
>
> Could you explain me why const is used here ?
const here, this is
ensured at least at syntax level.
OK.
[snip]
>Your transfer function has to handle this correctly:
> Then we call spi_sync then master->transfer. In this last function we have:
> list_for_each_entry (t, &mesg->transfers, transfer_list) {
> const u32 *txbuf = t->tx_buf; <--- point to zero when x[1] right ?????
> u32 *rxbuf = t->rx_buf; <--- point to zero when x[0] right ?????
> int i = 0;
> while(i < t->len >> 2) {
> rxbuf[i] = imx->xchg_single(imx, txbuf[i]);
> i++;
> }
> }
> What am I missing ???
while(i < t->len >> 2) {u32 txval = txbuf ? txbuf[i] : 0
u32 rxval = imx->xchg_single(imx, txval);
if (rxbuf)
rxbuf[i] = rxval;
i++;
}
That's what I was thinking about. The code above is from imx_spi.c. I am currently
writing an Altera spi driver that's why I was looking at this...
If no txbuf is available then simply transfer 0, if no rxbuf is
available then throw away the result.
BTW, I'm not sure if the above transfer-handler is able to handle 8bit
transfers correctly (because of len >> 2).
I agree.
Hope this helps.
Best Regards
Hubert
Thanks,
Franck.
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