spi: Add driver_override SPI device attribute

[linux-2.6-block.git] / drivers / spi / spi.c

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 2cfc3df821f6bf350d4b470c6feed2c7e54f61bf..fcbd4cfd28188b55aacc74a1690f77b16f0f9781 100644 (file)
--- 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;