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spi: bitbang: Make chipselect callback optional

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The ->chipselect() callback on the bit-banged SPI library
master is optional if using GPIO descriptors: when using
descriptors exclusively without any native chipselects,
the core does not even call out the the native ->set_cs()
and therefore ->chipselect() on a bit-banged SPI master
will not even be called in this case.

Make sure to respect the SPI_MASTER_GPIO_SS as used by
e.g. spi-gpio.c though: this setting will make the core
handle the chip select using GPIO descriptors *AND* call
the local chipselect handler.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20191205091340.59850-1-linus.walleij@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Linus Walleij 2019-12-05 10:13:40 +01:00 committed by Mark Brown
parent 8a6553ecdf
commit 4a07b8bcd5
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GPG Key ID: 24D68B725D5487D0
1 changed files with 19 additions and 2 deletions
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21
drivers/spi/spi-bitbang.c
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@ -329,8 +329,20 @@ static void spi_bitbang_set_cs(struct spi_device *spi, bool enable)
int spi_bitbang_init(struct spi_bitbang *bitbang)
{
struct spi_master *master = bitbang->master;
bool custom_cs;
if (!master || !bitbang->chipselect)
if (!master)
return -EINVAL;
/*
* We only need the chipselect callback if we are actually using it.
* If we just use GPIO descriptors, it is surplus. If the
* SPI_MASTER_GPIO_SS flag is set, we always need to call the
* driver-specific chipselect routine.
*/
custom_cs = (!master->use_gpio_descriptors ||
(master->flags & SPI_MASTER_GPIO_SS));
if (custom_cs && !bitbang->chipselect)
return -EINVAL;
mutex_init(&bitbang->lock);
@ -344,7 +356,12 @@ int spi_bitbang_init(struct spi_bitbang *bitbang)
master->prepare_transfer_hardware = spi_bitbang_prepare_hardware;
master->unprepare_transfer_hardware = spi_bitbang_unprepare_hardware;
master->transfer_one = spi_bitbang_transfer_one;
master->set_cs = spi_bitbang_set_cs;
/*
* When using GPIO descriptors, the ->set_cs() callback doesn't even
* get called unless SPI_MASTER_GPIO_SS is set.
*/
if (custom_cs)
master->set_cs = spi_bitbang_set_cs;
if (!bitbang->txrx_bufs) {
bitbang->use_dma = 0;