lkml.org 
[lkml]   [2008]   [Sep]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH 03/18] lirc driver for 1st-gen Media Center Ed. USB IR transceivers
Date
On Tuesday 09 September 2008 21:21:40 Jonathan Corbet wrote:
>
> > + * 2003_11_11 - Restructured to minimalize code interpretation in
> > the + * driver. The normal use case will be with lirc.
> > + *
> > + * 2004_01_01 - Removed all code interpretation. Generate mode2
> > data + * for passing off to lirc. Cleanup
> > + *
> > + * 2004_01_04 - Removed devfs handle. Put in a temporary
> > workaround + * for a known issue where repeats generate two
> > + * sequential spaces (last_was_repeat_gap)
> > + *
> > + * 2004_02_17 - Changed top level api to no longer use fops, and
> > + * instead use new interface for polling via
> > + * lirc_thread. Restructure data read/mode2 generation to
> > + * a single pass, reducing number of buffers. Rev to .2
> > + *
> > + * 2004_02_27 - Last of fixups to plugin->add_to_buf API. Properly
> > + * handle broken fragments from the receiver. Up the
> > + * sample rate and remove any pacing from
> > + * fetch_more_data. Fixes all known issues.
>
> General convention is that this sort of changelog information belongs
> in the SCM, not in the code. That's doubly true for the USB skeleton
> driver info.

I don't really care and I agree that the SCM is the preferred place for
the information. The only problem is that the info is in a different
SCM (lirc cvs repository).

I've removed the changelogs from all files as long as no names wre
mentioned.

> > +#include <linux/smp_lock.h>
>
> It doesn't look like this include is needed.

removed

> > +/* Structure to hold all of our device specific stuff */
> > +struct usb_skel {
>
> Perhaps renaming this structure to something more directly
> descriptive would make sense?

renamed to mceusb_device

> > + struct usb_device *udev; /* save off the usb device pointer */
> > + struct usb_interface *interface; /* the interface for this device
> > */ + unsigned char minor; /* the starting minor number for this
> > device */
>
> Minor numbers don't necessarily fit in an unsigned char.
>
> > + unsigned char num_ports; /* the number of ports this device has
> > */ + char num_interrupt_in; /* number of interrupt in endpoints */
> > + char num_bulk_in; /* number of bulk in endpoints */
> > + char num_bulk_out; /* number of bulk out endpoints */
> > +
> > + unsigned char *bulk_in_buffer; /* the buffer to receive data */
> > + int bulk_in_size; /* the size of the receive buffer */
> > + __u8 bulk_in_endpointAddr; /* the address of bulk in endpoint */
> > +
> > + unsigned char *bulk_out_buffer; /* the buffer to send data */
> > + int bulk_out_size; /* the size of the send buffer */
> > + struct urb *write_urb; /* the urb used to send data */
> > + __u8 bulk_out_endpointAddr; /* the address of bulk out endpoint
> > */ +
> > + atomic_t write_busy; /* true iff write urb is busy */
> > + struct completion write_finished; /* wait for the write to finish
> > */ +
> > + wait_queue_head_t wait_q; /* for timeouts */
> > + int open_count; /* number of times this port has been opened */
> > + struct mutex sem; /* locks this structure */
>
> "sem" is not a semaphore; it should probably have a different name.

renamed to lock

> > +static void mceusb_setup(struct usb_device *udev)
> > +{
> > + char data[8];
> > + int res;
> > +
> > + memset(data, 0, 8);
> > +
> > + /* Get Status */
> > + res = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
> > + USB_REQ_GET_STATUS, USB_DIR_IN,
> > + 0, 0, data, 2, HZ * 3);
>
> res is set many times in this function, but it is never checked. It
> seems to me like the addition of some error handling would be a good
> idea.

sigh, It would be a good idea, not sure if I'm motivated enough to add
that to a driver I can't test and I know almost nothing about.


> > + /* These two are sent by the windows driver, but stall for
> > + * me. I dont have an analyzer on the linux side so i can't
> > + * see what is actually different and why the device takes
> > + * issue with them
> > + */
>
> Hmm...how was that information obtained? If this driver was
> reverse-engineered, it would be good to know just what process was
> followed.

That's probably a question for the original author, Dan. CC added. I'm
just cleaning them up for kernel inclusion.

> > +static int msir_fetch_more_data(struct usb_skel *dev, int
> > dont_block) +{
>
> ...
>
> > + /* retry a few times on overruns; map all
> > + other errors to -EIO */
> > + if (retval) {
> > + if (retval == -EOVERFLOW && retries < 5) {
> > + retries++;
> > + interruptible_sleep_on_timeout(
> > + &dev->wait_q, HZ);
> > + continue;
>
> As others have noted, I think, getting new sleep_on() calls into the
> kernel is kind of a hard sell.

there are more, I'll fix them all before the next patchset get posted.

> ...
>
> > +
> > + /* select a "subminor" number (part of a minor number) */
> > + down(&minor_table_mutex);
>
> So...this driver has a mutex called "sem" and a semaphore called
> "minor_table_mutex". I suspect that minor_table_mutex should, in
> fact, be a mutex.

yes, the declaration looks like this:
static DECLARE_MUTEX(...);

which gives us a single holder semaphore. the static in front of
DECLARE_MUTEX() fools checkpatch. changed to to DEFINE_MUTEX, also in
two other drivers.

>
> ...
>
> > +error:
> > + mceusb_delete(dev);
> > + dev = NULL;
> > + dprintk("%s: retval = %x", __func__, retval);
> > + up(&minor_table_mutex);
> > + return retval;
> > +}
>
> This will leak the memory allocated for dev. It also leaves the
> entry in minor_table pointing to a nonfunctional device.

fixed.

Thanks for the review.

Janne



\
 
 \ /
  Last update: 2008-09-10 02:01    [from the cache]
©2003-2011 Jasper Spaans