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Date: Sun, 14 Feb 2021 12:57:06 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Alexandru Ardelean <alexandru.ardelean@...log.com>
Cc: <linux-kernel@...r.kernel.org>, <linux-iio@...r.kernel.org>,
<lars@...afoo.de>, <Michael.Hennerich@...log.com>,
<nuno.sa@...log.com>, <dragos.bogdan@...log.com>,
<rafael@...nel.org>, <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v5 05/17] iio: buffer: group attr count and attr alloc
On Thu, 11 Feb 2021 14:24:40 +0200
Alexandru Ardelean <alexandru.ardelean@...log.com> wrote:
> If we want to merge the attributes of the buffer/ and scan_elements/
> directories, we'll need to count all attributes first, then (depending on
> the attribute group) either allocate 2 attribute groups, or a single one.
> Historically an IIO buffer was described by 2 subdirectories under
> /sys/bus/iio/iio:devicesX (i.e. buffer/ and scan_elements/); these subdirs
> were actually 2 separate attribute groups on the iio_buffer object.
>
> Moving forward, if we want to allow more than one buffer per IIO device,
> keeping 2 subdirectories for each IIO buffer is a bit cumbersome
> (especially for userpace ABI). So, we will merge the attributes of these 2
> subdirs under a /sys/bus/iio/iio:devicesX/bufferY subdirectory. To do this,
> we need to count all attributes first, and then distribute them based on
> which buffer this is. For the first buffer, we'll need to also allocate the
> legacy 2 attribute groups (for buffer/ and scan_elements/), and also a
> /sys/bus/iio/iio:devicesX/buffer0 attribute group.
>
> For buffer1 and above, just a single attribute group will be allocated (the
> merged one).
>
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@...log.com>
One totally trivial thing noticed in here. If we happen to respin
please tidy it up, if I take these as is I 'might' tweak it, or I might
not bother depending on what mood I'm in later today.
Jonathan
> ---
> drivers/iio/industrialio-buffer.c | 71 ++++++++++++++++---------------
> 1 file changed, 37 insertions(+), 34 deletions(-)
>
> diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
> index cc846988fdb9..23f22be62cc7 100644
> --- a/drivers/iio/industrialio-buffer.c
> +++ b/drivers/iio/industrialio-buffer.c
> @@ -1257,41 +1257,16 @@ static int __iio_buffer_alloc_sysfs_and_mask(struct iio_buffer *buffer,
> {
> struct iio_dev_attr *p;
> struct attribute **attr;
> - int ret, i, attrn, attrcount;
> + int ret, i, attrn, scan_el_attrcount, buffer_attrcount;
> const struct iio_chan_spec *channels;
>
> - attrcount = 0;
> + buffer_attrcount = 0;
> if (buffer->attrs) {
> - while (buffer->attrs[attrcount] != NULL)
> - attrcount++;
> + while (buffer->attrs[buffer_attrcount] != NULL)
> + buffer_attrcount++;
> }
>
> - attr = kcalloc(attrcount + ARRAY_SIZE(iio_buffer_attrs) + 1,
> - sizeof(struct attribute *), GFP_KERNEL);
> - if (!attr)
> - return -ENOMEM;
> -
> - memcpy(attr, iio_buffer_attrs, sizeof(iio_buffer_attrs));
> - if (!buffer->access->set_length)
> - attr[0] = &dev_attr_length_ro.attr;
> -
> - if (buffer->access->flags & INDIO_BUFFER_FLAG_FIXED_WATERMARK)
> - attr[2] = &dev_attr_watermark_ro.attr;
> -
> - if (buffer->attrs)
> - memcpy(&attr[ARRAY_SIZE(iio_buffer_attrs)], buffer->attrs,
> - sizeof(struct attribute *) * attrcount);
> -
> - attr[attrcount + ARRAY_SIZE(iio_buffer_attrs)] = NULL;
> -
> - buffer->buffer_group.name = "buffer";
> - buffer->buffer_group.attrs = attr;
> -
> - ret = iio_device_register_sysfs_group(indio_dev, &buffer->buffer_group);
> - if (ret)
> - goto error_free_buffer_attrs;
> -
> - attrcount = 0;
> + scan_el_attrcount = 0;
> INIT_LIST_HEAD(&buffer->scan_el_dev_attr_list);
> channels = indio_dev->channels;
> if (channels) {
> @@ -1304,7 +1279,7 @@ static int __iio_buffer_alloc_sysfs_and_mask(struct iio_buffer *buffer,
> &channels[i]);
> if (ret < 0)
> goto error_cleanup_dynamic;
> - attrcount += ret;
> + scan_el_attrcount += ret;
> if (channels[i].type == IIO_TIMESTAMP)
> indio_dev->scan_index_timestamp =
> channels[i].scan_index;
> @@ -1319,9 +1294,37 @@ static int __iio_buffer_alloc_sysfs_and_mask(struct iio_buffer *buffer,
> }
> }
>
> + attr = kcalloc(buffer_attrcount + ARRAY_SIZE(iio_buffer_attrs) + 1,
> + sizeof(struct attribute *), GFP_KERNEL);
nitpick, I'd have made that sizeof(*attr)
> + if (!attr) {
> + ret = -ENOMEM;
> + goto error_free_scan_mask;
> + }
> +
> + memcpy(attr, iio_buffer_attrs, sizeof(iio_buffer_attrs));
> + if (!buffer->access->set_length)
> + attr[0] = &dev_attr_length_ro.attr;
> +
> + if (buffer->access->flags & INDIO_BUFFER_FLAG_FIXED_WATERMARK)
> + attr[2] = &dev_attr_watermark_ro.attr;
> +
> + if (buffer->attrs)
> + memcpy(&attr[ARRAY_SIZE(iio_buffer_attrs)], buffer->attrs,
> + sizeof(struct attribute *) * buffer_attrcount);
> +
> + buffer_attrcount += ARRAY_SIZE(iio_buffer_attrs);
> + attr[buffer_attrcount] = NULL;
> +
> + buffer->buffer_group.name = "buffer";
> + buffer->buffer_group.attrs = attr;
> +
> + ret = iio_device_register_sysfs_group(indio_dev, &buffer->buffer_group);
> + if (ret)
> + goto error_free_buffer_attrs;
> +
> buffer->scan_el_group.name = iio_scan_elements_group_name;
>
> - buffer->scan_el_group.attrs = kcalloc(attrcount + 1,
> + buffer->scan_el_group.attrs = kcalloc(scan_el_attrcount + 1,
> sizeof(buffer->scan_el_group.attrs[0]),
> GFP_KERNEL);
> if (buffer->scan_el_group.attrs == NULL) {
> @@ -1341,12 +1344,12 @@ static int __iio_buffer_alloc_sysfs_and_mask(struct iio_buffer *buffer,
>
> error_free_scan_el_attrs:
> kfree(buffer->scan_el_group.attrs);
> +error_free_buffer_attrs:
> + kfree(buffer->buffer_group.attrs);
> error_free_scan_mask:
> bitmap_free(buffer->scan_mask);
> error_cleanup_dynamic:
> iio_free_chan_devattr_list(&buffer->scan_el_dev_attr_list);
> -error_free_buffer_attrs:
> - kfree(buffer->buffer_group.attrs);
>
> return ret;
> }
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