spi: bitbang: Make chipselect callback optional (4a07b8bc) · Commits · 戴 / test

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>

drivers/spi/spi-bitbang.c

+19 −2

Original line number	Diff line number	Diff line
		@@ -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);
		@@ -344,6 +356,11 @@ 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;
		/*
		* 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) {

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