[PATCH v2 1/5] gnss: sirf: write data to gnss only when the gnss device is open

[Andreas Kemnade]

The api forbids writing data there otherwise. Prepare for the
serdev_open()/close() being a part of runtime pm.

Signed-off-by: Andreas Kemnade <andr...@kemnade.info>
---
Changes in v2:
 add locking

 drivers/gnss/sirf.c | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/gnss/sirf.c b/drivers/gnss/sirf.c
index 2c22836d3ffd..ba663de1db49 100644
--- a/drivers/gnss/sirf.c
+++ b/drivers/gnss/sirf.c
@@ -35,6 +35,12 @@ struct sirf_data {
        struct gpio_desc *wakeup;
        int irq;
        bool active;
+       /*
+        * There might be races between returning data and closing the gnss
+        * device.
+        */
+       struct mutex gdev_mutex;
+       bool opened;
        wait_queue_head_t power_wait;
 };
 
@@ -44,6 +50,7 @@ static int sirf_open(struct gnss_device *gdev)
        struct serdev_device *serdev = data->serdev;
        int ret;
 
+       data->opened = true;
        ret = serdev_device_open(serdev);
        if (ret)
                return ret;
@@ -55,6 +62,7 @@ static int sirf_open(struct gnss_device *gdev)
        if (ret < 0) {
                dev_err(&gdev->dev, "failed to runtime resume: %d\n", ret);
                pm_runtime_put_noidle(&serdev->dev);
+               data->opened = false;
                goto err_close;
        }
 
@@ -74,6 +82,9 @@ static void sirf_close(struct gnss_device *gdev)
        serdev_device_close(serdev);
 
        pm_runtime_put(&serdev->dev);
+       mutex_lock(&data->gdev_mutex);
+       data->opened = false;
+       mutex_unlock(&data->gdev_mutex);
 }
 
 static int sirf_write_raw(struct gnss_device *gdev, const unsigned char *buf,
@@ -105,8 +116,22 @@ static int sirf_receive_buf(struct serdev_device *serdev,
 {
        struct sirf_data *data = serdev_device_get_drvdata(serdev);
        struct gnss_device *gdev = data->gdev;
+       int ret = 0;
+
+       /*
+        * we might come here everytime when runtime is resumed
+        * and data is received. Two cases are possible
+        * 1. device is opened during initialisation
+        * 2. kernel is compiled without runtime pm
+        *    and device is opened all the time
+        */
+       mutex_lock(&data->gdev_mutex);
+       if (data->opened)
+               ret = gnss_insert_raw(gdev, buf, count);
 
-       return gnss_insert_raw(gdev, buf, count);
+       mutex_unlock(&data->gdev_mutex);
+
+       return ret;
 }
 
 static const struct serdev_device_ops sirf_serdev_ops = {
@@ -275,6 +300,7 @@ static int sirf_probe(struct serdev_device *serdev)
        data->serdev = serdev;
        data->gdev = gdev;
 
+       mutex_init(&data->gdev_mutex);
        init_waitqueue_head(&data->power_wait);
 
        serdev_device_set_drvdata(serdev, data);
-- 
2.11.0