On 28/03/15 12:24, Jonathan Cameron wrote:
> On 22/03/15 18:33, Octavian Purdila wrote:
>> From: Josselin Costanzi <josselin.costanzi@xxxxxxxxxxxxxxxxx>
>>
>> Currently the IIO buffer blocking read only wait until at least one
>> data element is available.
>> This patch makes the reader sleep until enough data is collected before
>> returning to userspace. This should limit the read() calls count when
>> trying to get data in batches.
>>
>> Co-author: Yannick Bedhomme <yannick.bedhomme@xxxxxxxxxxxxxxxxx>
>> Signed-off-by: Josselin Costanzi <josselin.costanzi@xxxxxxxxxxxxxxxxx>
>> [rebased and remove buffer timeout]
>> Signed-off-by: Octavian Purdila <octavian.purdila@xxxxxxxxx>
> Great. Applied to the togreg branch of iio.git - initially pushed out as
> testing for the autobuilders to try their best to break things.
The autobuilder threw up the following:
drivers/iio/industrialio-buffer.c:110 iio_buffer_read_first_n_outer() warn: variable dereferenced before check 'rb' (see line 102)
Fix is fairly obvious:
Fixup for add watermark logic
---------------------- drivers/iio/industrialio-buffer.c ----------------------
index 87142bb0f010..df919f44d513 100644
@@ -99,7 +99,7 @@ ssize_t iio_buffer_read_first_n_outer(struct file *filp, char __user *buf,
{
struct iio_dev *indio_dev = filp->private_data;
struct iio_buffer *rb = indio_dev->buffer;
- size_t datum_size = rb->bytes_per_datum;
+ size_t datum_size;
size_t to_wait = 0;
size_t to_read;
int ret;
@@ -110,6 +110,8 @@ ssize_t iio_buffer_read_first_n_outer(struct file *filp, char __user *buf,
if (!rb || !rb->access->read_first_n)
return -EINVAL;
+ datum_size = rb->bytes_per_datum;
+
/*
* If datum_size is 0 there will never be anything to read from the
* buffer, so signal end of file now.
So I'll just merge it into the original patch unless someone shouts that I've
messed it up!
>
> Jonathan
>> ---
>> Documentation/ABI/testing/sysfs-bus-iio | 15 ++++
>> drivers/iio/industrialio-buffer.c | 118 +++++++++++++++++++++++++++----
>> drivers/iio/kfifo_buf.c | 11 ++-
>> drivers/staging/iio/accel/sca3000_ring.c | 4 +-
>> include/linux/iio/buffer.h | 8 ++-
>> 5 files changed, 129 insertions(+), 27 deletions(-)
>>
>> diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
>> index 6be17c2..0051641 100644
>> --- a/Documentation/ABI/testing/sysfs-bus-iio
>> +++ b/Documentation/ABI/testing/sysfs-bus-iio
>> @@ -1273,3 +1273,18 @@ Contact: linux-iio@xxxxxxxxxxxxxxx
>> Description:
>> Specifies number of seconds in which we compute the steps
>> that occur in order to decide if the consumer is making steps.
>> +
>> +What: /sys/bus/iio/devices/iio:deviceX/buffer/watermark
>> +KernelVersion: 4.2
>> +Contact: linux-iio@xxxxxxxxxxxxxxx
>> +Description:
>> + A single positive integer specifying the maximum number of scan
>> + elements to wait for.
>> + Poll will block until the watermark is reached.
>> + Blocking read will wait until the minimum between the requested
>> + read amount or the low water mark is available.
>> + Non-blocking read will retrieve the available samples from the
>> + buffer even if there are less samples then watermark level. This
>> + allows the application to block on poll with a timeout and read
>> + the available samples after the timeout expires and thus have a
>> + maximum delay guarantee.
>> diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
>> index c2d5440..a4f4f07 100644
>> --- a/drivers/iio/industrialio-buffer.c
>> +++ b/drivers/iio/industrialio-buffer.c
>> @@ -37,11 +37,28 @@ static bool iio_buffer_is_active(struct iio_buffer *buf)
>> return !list_empty(&buf->buffer_list);
>> }
>>
>> -static bool iio_buffer_data_available(struct iio_buffer *buf)
>> +static size_t iio_buffer_data_available(struct iio_buffer *buf)
>> {
>> return buf->access->data_available(buf);
>> }
>>
>> +static bool iio_buffer_ready(struct iio_dev *indio_dev, struct iio_buffer *buf,
>> + size_t to_wait)
>> +{
>> + /* wakeup if the device was unregistered */
>> + if (!indio_dev->info)
>> + return true;
>> +
>> + /* drain the buffer if it was disabled */
>> + if (!iio_buffer_is_active(buf))
>> + to_wait = min_t(size_t, to_wait, 1);
>> +
>> + if (iio_buffer_data_available(buf) >= to_wait)
>> + return true;
>> +
>> + return false;
>> +}
>> +
>> /**
>> * iio_buffer_read_first_n_outer() - chrdev read for buffer access
>> *
>> @@ -53,6 +70,8 @@ ssize_t iio_buffer_read_first_n_outer(struct file *filp, char __user *buf,
>> {
>> struct iio_dev *indio_dev = filp->private_data;
>> struct iio_buffer *rb = indio_dev->buffer;
>> + size_t datum_size = rb->bytes_per_datum;
>> + size_t to_wait = 0;
>> int ret;
>>
>> if (!indio_dev->info)
>> @@ -61,19 +80,24 @@ ssize_t iio_buffer_read_first_n_outer(struct file *filp, char __user *buf,
>> if (!rb || !rb->access->read_first_n)
>> return -EINVAL;
>>
>> + /*
>> + * If datum_size is 0 there will never be anything to read from the
>> + * buffer, so signal end of file now.
>> + */
>> + if (!datum_size)
>> + return 0;
>> +
>> + if (!(filp->f_flags & O_NONBLOCK))
>> + to_wait = min_t(size_t, n / datum_size, rb->watermark);
>> +
>> do {
>> - if (!iio_buffer_data_available(rb)) {
>> - if (filp->f_flags & O_NONBLOCK)
>> - return -EAGAIN;
>> + ret = wait_event_interruptible(rb->pollq,
>> + iio_buffer_ready(indio_dev, rb, to_wait));
>> + if (ret)
>> + return ret;
>>
>> - ret = wait_event_interruptible(rb->pollq,
>> - iio_buffer_data_available(rb) ||
>> - indio_dev->info == NULL);
>> - if (ret)
>> - return ret;
>> - if (indio_dev->info == NULL)
>> - return -ENODEV;
>> - }
>> + if (!indio_dev->info)
>> + return -ENODEV;
>>
>> ret = rb->access->read_first_n(rb, n, buf);
>> if (ret == 0 && (filp->f_flags & O_NONBLOCK))
>> @@ -96,9 +120,8 @@ unsigned int iio_buffer_poll(struct file *filp,
>> return -ENODEV;
>>
>> poll_wait(filp, &rb->pollq, wait);
>> - if (iio_buffer_data_available(rb))
>> + if (iio_buffer_ready(indio_dev, rb, rb->watermark))
>> return POLLIN | POLLRDNORM;
>> - /* need a way of knowing if there may be enough data... */
>> return 0;
>> }
>>
>> @@ -123,6 +146,7 @@ void iio_buffer_init(struct iio_buffer *buffer)
>> INIT_LIST_HEAD(&buffer->buffer_list);
>> init_waitqueue_head(&buffer->pollq);
>> kref_init(&buffer->ref);
>> + buffer->watermark = 1;
>> }
>> EXPORT_SYMBOL(iio_buffer_init);
>>
>> @@ -416,6 +440,11 @@ static ssize_t iio_buffer_write_length(struct device *dev,
>> buffer->access->set_length(buffer, val);
>> ret = 0;
>> }
>> + if (ret)
>> + goto out;
>> + if (buffer->length && buffer->length < buffer->watermark)
>> + buffer->watermark = buffer->length;
>> +out:
>> mutex_unlock(&indio_dev->mlock);
>>
>> return ret ? ret : len;
>> @@ -472,6 +501,7 @@ static void iio_buffer_activate(struct iio_dev *indio_dev,
>> static void iio_buffer_deactivate(struct iio_buffer *buffer)
>> {
>> list_del_init(&buffer->buffer_list);
>> + wake_up_interruptible(&buffer->pollq);
>> iio_buffer_put(buffer);
>> }
>>
>> @@ -754,16 +784,64 @@ done:
>>
>> static const char * const iio_scan_elements_group_name = "scan_elements";
>>
>> +static ssize_t iio_buffer_show_watermark(struct device *dev,
>> + struct device_attribute *attr,
>> + char *buf)
>> +{
>> + struct iio_dev *indio_dev = dev_to_iio_dev(dev);
>> + struct iio_buffer *buffer = indio_dev->buffer;
>> +
>> + return sprintf(buf, "%u\n", buffer->watermark);
>> +}
>> +
>> +static ssize_t iio_buffer_store_watermark(struct device *dev,
>> + struct device_attribute *attr,
>> + const char *buf,
>> + size_t len)
>> +{
>> + struct iio_dev *indio_dev = dev_to_iio_dev(dev);
>> + struct iio_buffer *buffer = indio_dev->buffer;
>> + unsigned int val;
>> + int ret;
>> +
>> + ret = kstrtouint(buf, 10, &val);
>> + if (ret)
>> + return ret;
>> + if (!val)
>> + return -EINVAL;
>> +
>> + mutex_lock(&indio_dev->mlock);
>> +
>> + if (val > buffer->length) {
>> + ret = -EINVAL;
>> + goto out;
>> + }
>> +
>> + if (iio_buffer_is_active(indio_dev->buffer)) {
>> + ret = -EBUSY;
>> + goto out;
>> + }
>> +
>> + buffer->watermark = val;
>> +out:
>> + mutex_unlock(&indio_dev->mlock);
>> +
>> + return ret ? ret : len;
>> +}
>> +
>> static DEVICE_ATTR(length, S_IRUGO | S_IWUSR, iio_buffer_read_length,
>> iio_buffer_write_length);
>> static struct device_attribute dev_attr_length_ro = __ATTR(length,
>> S_IRUGO, iio_buffer_read_length, NULL);
>> static DEVICE_ATTR(enable, S_IRUGO | S_IWUSR,
>> iio_buffer_show_enable, iio_buffer_store_enable);
>> +static DEVICE_ATTR(watermark, S_IRUGO | S_IWUSR,
>> + iio_buffer_show_watermark, iio_buffer_store_watermark);
>>
>> static struct attribute *iio_buffer_attrs[] = {
>> &dev_attr_length.attr,
>> &dev_attr_enable.attr,
>> + &dev_attr_watermark.attr,
>> };
>>
>> int iio_buffer_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
>> @@ -944,8 +1022,18 @@ static const void *iio_demux(struct iio_buffer *buffer,
>> static int iio_push_to_buffer(struct iio_buffer *buffer, const void *data)
>> {
>> const void *dataout = iio_demux(buffer, data);
>> + int ret;
>> +
>> + ret = buffer->access->store_to(buffer, dataout);
>> + if (ret)
>> + return ret;
>>
>> - return buffer->access->store_to(buffer, dataout);
>> + /*
>> + * We can't just test for watermark to decide if we wake the poll queue
>> + * because read may request less samples than the watermark.
>> + */
>> + wake_up_interruptible_poll(&buffer->pollq, POLLIN | POLLRDNORM);
>> + return 0;
>> }
>>
>> static void iio_buffer_demux_free(struct iio_buffer *buffer)
>> diff --git a/drivers/iio/kfifo_buf.c b/drivers/iio/kfifo_buf.c
>> index b2beea0..847ca56 100644
>> --- a/drivers/iio/kfifo_buf.c
>> +++ b/drivers/iio/kfifo_buf.c
>> @@ -83,9 +83,6 @@ static int iio_store_to_kfifo(struct iio_buffer *r,
>> ret = kfifo_in(&kf->kf, data, 1);
>> if (ret != 1)
>> return -EBUSY;
>> -
>> - wake_up_interruptible_poll(&r->pollq, POLLIN | POLLRDNORM);
>> -
>> return 0;
>> }
>>
>> @@ -109,16 +106,16 @@ static int iio_read_first_n_kfifo(struct iio_buffer *r,
>> return copied;
>> }
>>
>> -static bool iio_kfifo_buf_data_available(struct iio_buffer *r)
>> +static size_t iio_kfifo_buf_data_available(struct iio_buffer *r)
>> {
>> struct iio_kfifo *kf = iio_to_kfifo(r);
>> - bool empty;
>> + size_t samples;
>>
>> mutex_lock(&kf->user_lock);
>> - empty = kfifo_is_empty(&kf->kf);
>> + samples = kfifo_len(&kf->kf);
>> mutex_unlock(&kf->user_lock);
>>
>> - return !empty;
>> + return samples;
>> }
>>
>> static void iio_kfifo_buffer_release(struct iio_buffer *buffer)
>> diff --git a/drivers/staging/iio/accel/sca3000_ring.c b/drivers/staging/iio/accel/sca3000_ring.c
>> index f76a268..8589ead 100644
>> --- a/drivers/staging/iio/accel/sca3000_ring.c
>> +++ b/drivers/staging/iio/accel/sca3000_ring.c
>> @@ -129,9 +129,9 @@ error_ret:
>> return ret ? ret : num_read;
>> }
>>
>> -static bool sca3000_ring_buf_data_available(struct iio_buffer *r)
>> +static size_t sca3000_ring_buf_data_available(struct iio_buffer *r)
>> {
>> - return r->stufftoread;
>> + return r->stufftoread ? r->watermark : 0;
>> }
>>
>> /**
>> diff --git a/include/linux/iio/buffer.h b/include/linux/iio/buffer.h
>> index b65850a..eb8622b 100644
>> --- a/include/linux/iio/buffer.h
>> +++ b/include/linux/iio/buffer.h
>> @@ -21,8 +21,8 @@ struct iio_buffer;
>> * struct iio_buffer_access_funcs - access functions for buffers.
>> * @store_to: actually store stuff to the buffer
>> * @read_first_n: try to get a specified number of bytes (must exist)
>> - * @data_available: indicates whether data for reading from the buffer is
>> - * available.
>> + * @data_available: indicates how much data is available for reading from
>> + * the buffer.
>> * @request_update: if a parameter change has been marked, update underlying
>> * storage.
>> * @set_bytes_per_datum:set number of bytes per datum
>> @@ -43,7 +43,7 @@ struct iio_buffer_access_funcs {
>> int (*read_first_n)(struct iio_buffer *buffer,
>> size_t n,
>> char __user *buf);
>> - bool (*data_available)(struct iio_buffer *buffer);
>> + size_t (*data_available)(struct iio_buffer *buffer);
>>
>> int (*request_update)(struct iio_buffer *buffer);
>>
>> @@ -72,6 +72,7 @@ struct iio_buffer_access_funcs {
>> * @demux_bounce: [INTERN] buffer for doing gather from incoming scan.
>> * @buffer_list: [INTERN] entry in the devices list of current buffers.
>> * @ref: [INTERN] reference count of the buffer.
>> + * @watermark: [INTERN] number of datums to wait for poll/read.
>> */
>> struct iio_buffer {
>> int length;
>> @@ -90,6 +91,7 @@ struct iio_buffer {
>> void *demux_bounce;
>> struct list_head buffer_list;
>> struct kref ref;
>> + unsigned int watermark;
>> };
>>
>> /**
>>
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-iio" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
--
To unsubscribe from this list: send the line "unsubscribe linux-iio" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
