Hi Sebastian,
Thank you for the patch.
On Friday, 13 July 2018 01:35:27 EEST Sebastian Andrzej Siewior wrote:
> Provide usb_fill_iso_urb() for the initialisation of isochronous URBs.
> We already have one of this helpers for control, bulk and interruptible
> URB types. This helps to keep the initialisation of the URB members in
> one place.
> Update the documentation by adding this to the available init functions
> and remove the suggestion to use the `_int_' helper which might provide
> wrong encoding for the `interval' member.
>
> This looks like it would cover most users nicely. The sound subsystem
> initialises the ->iso_frame_desc[].offset + length member (often) at a
> different location and I'm not sure ->interval will work always as
> expected. So we might need to overwrite those two in worst case.
>
> Some users also initialise ->iso_frame_desc[].actual_length but I don't
s/I don't/I don't think/ ?
> this is required since it is the return value.
>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> ---
> Documentation/driver-api/usb/URB.rst | 12 +++----
> include/linux/usb.h | 53 ++++++++++++++++++++++++++++
> 2 files changed, 59 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/driver-api/usb/URB.rst
> b/Documentation/driver-api/usb/URB.rst index 61a54da9fce9..20030b781519
> 100644
> --- a/Documentation/driver-api/usb/URB.rst
> +++ b/Documentation/driver-api/usb/URB.rst
> @@ -116,11 +116,11 @@ What has to be filled in?
>
> Depending on the type of transaction, there are some inline functions
> defined in ``linux/usb.h`` to simplify the initialization, such as
> -:c:func:`usb_fill_control_urb`, :c:func:`usb_fill_bulk_urb` and
> -:c:func:`usb_fill_int_urb`. In general, they need the usb device pointer,
> -the pipe (usual format from usb.h), the transfer buffer, the desired
> transfer -length, the completion handler, and its context. Take a look at
> the some -existing drivers to see how they're used.
> +:c:func:`usb_fill_control_urb`, :c:func:`usb_fill_bulk_urb`,
> +:c:func:`usb_fill_int_urb` and :c:func:`usb_fill_iso_urb`. In general,
> they +need the usb device pointer, the pipe (usual format from usb.h), the
> transfer +buffer, the desired transfer length, the completion handler, and
> its context. +Take a look at the some existing drivers to see how they're
> used.
>
> Flags:
>
> @@ -243,7 +243,7 @@ Besides the fields present on a bulk transfer, for ISO,
> you also also have to set ``urb->interval`` to say how often to make
> transfers; it's often one per frame (which is once every microframe for
> highspeed devices). The actual interval used will be a power of two that's
> no bigger than what -you specify. You can use the
> :c:func:`usb_fill_int_urb` macro to fill +you specify. You can use the
> :c:func:`usb_fill_iso_urb` macro to fill most ISO transfer fields.
>
> For ISO transfers you also have to fill a
> :c:type:`usb_iso_packet_descriptor` diff --git a/include/linux/usb.h
> b/include/linux/usb.h
> index 4cdd515a4385..74a3339041d6 100644
> --- a/include/linux/usb.h
> +++ b/include/linux/usb.h
> @@ -1697,6 +1697,59 @@ static inline void usb_fill_int_urb(struct urb *urb,
> urb->start_frame = -1;
> }
>
> +/**
> + * usb_fill_iso_urb - macro to help initialize an isochronous urb
Strictly speaking this isn't a macro, so I'd write "initializes an isochronous
urb"
> + * @urb: pointer to the urb to initialize.
> + * @dev: pointer to the struct usb_device for this urb.
> + * @pipe: the endpoint pipe
> + * @transfer_buffer: pointer to the transfer buffer
> + * @buffer_length: length of the transfer buffer
> + * @complete_fn: pointer to the usb_complete_t function
> + * @context: what to set the urb context to.
> + * @interval: what to set the urb interval to, encoded like
> + * the endpoint descriptor's bInterval value.
> + * @packets: number of ISO packets.
> + * @packet_size: size of each ISO packet.
> + *
> + * Initializes an isochronous urb with the proper information needed to
> submit
> + * it to a device.
> + *
> + * Note that isochronous endpoints use a logarithmic encoding of the
> endpoint
> + * interval, and express polling intervals in microframes (eight per
> + * millisecond) rather than in frames (one per millisecond).
> + */
> +static inline void usb_fill_iso_urb(struct urb *urb,
> + struct usb_device *dev,
> + unsigned int pipe,
> + void *transfer_buffer,
> + int buffer_length,
> + usb_complete_t complete_fn,
> + void *context,
> + int interval,
> + unsigned int packets,
> + unsigned int packet_size)
> +{
> + unsigned int i;
> +
> + urb->dev = dev;
> + urb->pipe = pipe;
> + urb->transfer_buffer = transfer_buffer;
> + urb->transfer_buffer_length = buffer_length;
> + urb->complete = complete_fn;
> + urb->context = context;
> +
> + interval = clamp(interval, 1, 16);
> + urb->interval = 1 << (interval - 1);
> + urb->start_frame = -1;
> +
> + urb->number_of_packets = packets;
> +
> + for (i = 0; i < packets; i++) {
> + urb->iso_frame_desc[i].offset = packet_size * i;
> + urb->iso_frame_desc[i].length = packet_size;
> + }
> +}
I think this should be moved to a .c file as the function is growing big, but
that's true of the other URB helpers as well, so it can be done later in a
separate patch.
Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> extern void usb_init_urb(struct urb *urb);
> extern struct urb *usb_alloc_urb(int iso_packets, gfp_t mem_flags);
> extern void usb_free_urb(struct urb *urb);
--
Regards,
Laurent Pinchart
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