From 5039563e7c25eccd7fec1de6706011009d1c5665 Mon Sep 17 00:00:00 2001 From: Trent Piepho Date: Thu, 20 Sep 2018 19:18:32 +0000 Subject: [PATCH] spi: Add driver_override SPI device attribute MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit This attribute works the same was as the identically named attribute for PCI, AMBA, and platform devices. For reference, see: commit 3cf385713460 ("ARM: 8256/1: driver coamba: add device binding path 'driver_override'") commit 3d713e0e382e ("driver core: platform: add device binding path 'driver_override'") commit 782a985d7af2 ("PCI: Introduce new device binding path using pci_dev.driver_override") If the name of a driver is written to this attribute, then the device will bind to the named driver and only the named driver. The device will bind to the driver even if the driver does not list the device in its id table. This behavior is different than the driver's bind attribute, which only allows binding to devices that are listed as supported by the driver. It can be used to bind a generic driver, like spidev, to a device. Signed-off-by: Trent Piepho Reviewed-by: Jan Kundrát Tested-by: Jan Kundrát Reviewed-by: Geert Uytterhoeven Signed-off-by: Mark Brown --- drivers/spi/spi.c | 51 +++++++++++++++++++++++++++++++++++++++++ include/linux/spi/spi.h | 1 + 2 files changed, 52 insertions(+) diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index 2cfc3df821f6..fcbd4cfd2818 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -51,6 +51,7 @@ static void spidev_release(struct device *dev) spi->controller->cleanup(spi); spi_controller_put(spi->controller); + kfree(spi->driver_override); kfree(spi); } @@ -68,6 +69,51 @@ modalias_show(struct device *dev, struct device_attribute *a, char *buf) } static DEVICE_ATTR_RO(modalias); +static ssize_t driver_override_store(struct device *dev, + struct device_attribute *a, + const char *buf, size_t count) +{ + struct spi_device *spi = to_spi_device(dev); + const char *end = memchr(buf, '\n', count); + const size_t len = end ? end - buf : count; + const char *driver_override, *old; + + /* We need to keep extra room for a newline when displaying value */ + if (len >= (PAGE_SIZE - 1)) + return -EINVAL; + + driver_override = kstrndup(buf, len, GFP_KERNEL); + if (!driver_override) + return -ENOMEM; + + device_lock(dev); + old = spi->driver_override; + if (len) { + spi->driver_override = driver_override; + } else { + /* Emptry string, disable driver override */ + spi->driver_override = NULL; + kfree(driver_override); + } + device_unlock(dev); + kfree(old); + + return count; +} + +static ssize_t driver_override_show(struct device *dev, + struct device_attribute *a, char *buf) +{ + const struct spi_device *spi = to_spi_device(dev); + ssize_t len; + + device_lock(dev); + len = snprintf(buf, PAGE_SIZE, "%s\n", spi->driver_override ? : ""); + device_unlock(dev); + return len; +} +static DEVICE_ATTR_RW(driver_override); + #define SPI_STATISTICS_ATTRS(field, file) \ static ssize_t spi_controller_##field##_show(struct device *dev, \ struct device_attribute *attr, \ @@ -149,6 +195,7 @@ SPI_STATISTICS_SHOW(transfers_split_maxsize, "%lu"); static struct attribute *spi_dev_attrs[] = { &dev_attr_modalias.attr, + &dev_attr_driver_override.attr, NULL, }; @@ -296,6 +343,10 @@ static int spi_match_device(struct device *dev, struct device_driver *drv) const struct spi_device *spi = to_spi_device(dev); const struct spi_driver *sdrv = to_spi_driver(drv); + /* Check override first, and if set, only use the named driver */ + if (spi->driver_override) + return strcmp(spi->driver_override, drv->name) == 0; + /* Attempt an OF style match */ if (of_driver_match_device(dev, drv)) return 1; diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index f08824ea1968..3de9958ca28b 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -159,6 +159,7 @@ struct spi_device { void *controller_state; void *controller_data; char modalias[SPI_NAME_SIZE]; + const char *driver_override; int cs_gpio; /* chip select gpio */ /* the statistics */ -- 2.30.2