| Message ID | 1428591822-24279-2-git-send-email-per.nilsson@xelmo.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Apr 09, 2015 at 05:03:42PM +0200, Pelle Nilsson wrote: > This callback is mandatory since txrx_bufs callback is defined. The lack of > it causes a kernel panic on first SPI transaction. Why is the callback mandatory if an empty implementation is OK?
On 2015-04-09 17:40, Mark Brown wrote:
> Why is the callback mandatory if an empty implementation is OK?
Ask the author of spi-bitbang. :-)
In spi_bitbang_start() we have this chunk of code:
if (!bitbang->txrx_bufs) {
bitbang->use_dma = 0;
bitbang->txrx_bufs = spi_bitbang_bufs;
if (!master->setup) {
if (!bitbang->setup_transfer)
bitbang->setup_transfer =
spi_bitbang_setup_transfer;
master->setup = spi_bitbang_setup;
master->cleanup = spi_bitbang_cleanup;
}
}
As can be seen here, if setup_transfer is NULL (not set by the
specific driver), it is filled in with the default callback function
spi_bitbang_setup_transfer(), but only if txrx_bufs is also NULL,
which is not the case here.
There is a comment in spi-xilinx also stating this fact (though their
implementation isn't actually empty anymore):
/* spi_bitbang requires custom setup_transfer() to be defined if there
is a
* custom txrx_bufs().
*/
--
To unsubscribe from this list: send the line "unsubscribe linux-spi" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Apr 09, 2015 at 05:50:52PM +0200, Pelle Nilsson wrote: > On 2015-04-09 17:40, Mark Brown wrote: > > Why is the callback mandatory if an empty implementation is OK? > Ask the author of spi-bitbang. :-) What I'm trying to suggest is that you're perhaps fixing the wrong problem - make the callback optional if there's a good reason for it. Why is this patch the best fix?
On 2015-04-09 18:10, Mark Brown wrote: > On Thu, Apr 09, 2015 at 05:50:52PM +0200, Pelle Nilsson wrote: What > I'm trying to suggest is that you're perhaps fixing the wrong > problem - make the callback optional if there's a good reason for > it. Yes, the callback can be made optional, I'll send a new patch. -- To unsubscribe from this list: send the line "unsubscribe linux-spi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/spi/spi-altera.c b/drivers/spi/spi-altera.c index b95010e..6d72b1d 100644 --- a/drivers/spi/spi-altera.c +++ b/drivers/spi/spi-altera.c @@ -197,6 +197,11 @@ static irqreturn_t altera_spi_irq(int irq, void *dev) return IRQ_HANDLED; } +static int altera_spi_setupxfer(struct spi_device *spi, struct spi_transfer *t) +{ + return 0; +} + static int altera_spi_probe(struct platform_device *pdev) { struct altera_spi *hw; @@ -220,6 +225,7 @@ static int altera_spi_probe(struct platform_device *pdev) /* setup the state for the bitbang driver */ hw->bitbang.master = master; + hw->bitbang.setup_transfer = altera_spi_setupxfer; hw->bitbang.chipselect = altera_spi_chipsel; hw->bitbang.txrx_bufs = altera_spi_txrx;
This callback is mandatory since txrx_bufs callback is defined. The lack of it causes a kernel panic on first SPI transaction. Signed-off-by: Pelle Nilsson <per.nilsson@xelmo.com> --- drivers/spi/spi-altera.c | 6 ++++++ 1 file changed, 6 insertions(+)