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spi: allow ancillary devices to share parent's chip selects

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When registering an ancillary SPI device, the current code flags a chip
select conflict with the parent device. This happens because the
ancillary device intentionally uses one of the parent's chip selects,
but __spi_add_device() checks against all existing devices including
the parent.

Allow this by passing the parent device pointer to __spi_add_device()
and skipping the conflict check when the existing device is the parent.

Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/bcb1eb34fc5e86fd5dbb4472ad1d3ea3cf3e9779.1770393792.git.antoniu.miclaus@analog.com
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Antoniu Miclaus 2026-02-06 18:07:13 +02:00 committed by Mark Brown
parent 6de23f81a5
commit ffef412304
No known key found for this signature in database
GPG Key ID: 24D68B725D5487D0
1 changed files with 23 additions and 6 deletions
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29
drivers/spi/spi.c
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@ -641,12 +641,26 @@ static inline int spi_dev_check_cs(struct device *dev,
return 0;
}
struct spi_dev_check_info {
struct spi_device *new_spi;
struct spi_device *parent; /* set for ancillary devices */
};
static int spi_dev_check(struct device *dev, void *data)
{
struct spi_device *spi = to_spi_device(dev);
struct spi_device *new_spi = data;
struct spi_dev_check_info *info = data;
struct spi_device *new_spi = info->new_spi;
int status, idx;
/*
* When registering an ancillary device, skip checking against the
* parent device since the ancillary is intentionally using one of
* the parent's chip selects.
*/
if (info->parent && spi == info->parent)
return 0;
if (spi->controller == new_spi->controller) {
for (idx = 0; idx < spi->num_chipselect; idx++) {
status = spi_dev_check_cs(dev, spi, idx, new_spi, 0);
@ -663,10 +677,11 @@ static void spi_cleanup(struct spi_device *spi)
spi->controller->cleanup(spi);
}
static int __spi_add_device(struct spi_device *spi)
static int __spi_add_device(struct spi_device *spi, struct spi_device *parent)
{
struct spi_controller *ctlr = spi->controller;
struct device *dev = ctlr->dev.parent;
struct spi_dev_check_info check_info;
int status, idx;
u8 cs;
@ -710,7 +725,9 @@ static int __spi_add_device(struct spi_device *spi)
* chipselect **BEFORE** we call setup(), else we'll trash
* its configuration.
*/
status = bus_for_each_dev(&spi_bus_type, NULL, spi, spi_dev_check);
check_info.new_spi = spi;
check_info.parent = parent;
status = bus_for_each_dev(&spi_bus_type, NULL, &check_info, spi_dev_check);
if (status)
return status;
@ -772,7 +789,7 @@ int spi_add_device(struct spi_device *spi)
spi_dev_set_name(spi);
mutex_lock(&ctlr->add_lock);
status = __spi_add_device(spi);
status = __spi_add_device(spi, NULL);
mutex_unlock(&ctlr->add_lock);
return status;
}
@ -2715,8 +2732,8 @@ struct spi_device *spi_new_ancillary_device(struct spi_device *spi,
WARN_ON(!mutex_is_locked(&ctlr->add_lock));
/* Register the new device */
rc = __spi_add_device(ancillary);
/* Register the new device, passing the parent to skip CS conflict check */
rc = __spi_add_device(ancillary, spi);
if (rc) {
dev_err(&spi->dev, "failed to register ancillary device\n");
goto err_out;