Messages in this thread | | | From | Oliver Neukum <> | Subject | Re: [PATCH] USB: add USB test and measurement class driver - round 2 | Date | Thu, 28 Aug 2008 23:29:33 +0200 |
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> > > + buffer[4] = (this_part - 12 - 3) & 255; > > > + buffer[5] = ((this_part - 12 - 3) >> 8) & 255; > > > + buffer[6] = ((this_part - 12 - 3) >> 16) & 255; > > > + buffer[7] = ((this_part - 12 - 3) >> 24) & 255; > > > > We have excellent endianness conversion macros. > > For splitting values up into the individual byte portions? I think this > is far more obvious as to exactly what is going on, don't you?
No. Kernel code does not exist to show how to do endianness conversion. We have clearly labeled functions.
> > > + buffer[8] = data->TermCharEnabled * 2; > > > + /* Use term character? */ > > > > smp_rmb(); /* we must make sure we don't read a stale terminator */ > > I'm not going to worry about races here, that's not a real issue.
There is no such thing as an ignorable race. On second thought you can take the mutex in the sysfs handlers. That will also do the job.
> > This and usbtmc_read() need a test for disconnection. Open() and disconnect > > are guarded in usbcore, read & write are not. By reference count you've made > > sure you have a valid device descriptor, but the device may have been reprobed. > > If so, then struct usb_device would be different, right? Oh, I see, > disconnect() using usbfs/sysfs. Bah, is it really something that > happens in the real world? Oh well, I'll go fix this...
This is oopsable from user space.
> > If you ignore an error return, be open about it. > > I'm not? Should I print an error and then just continue on? Would that > be sufficient?
Yes.
> > > +static void usbtmc_disconnect(struct usb_interface *intf) > > > +{ > > > + struct usbtmc_device_data *data; > > > + > > > + dev_dbg(&intf->dev, "usbtmc_disconnect called\n"); > > > + > > > > You must set a flag for read, write and ioctl. > > Will do. Then I need to lock the flag with a mutex, right?
Yes. You can set the intf pointer to NULL. That's sort of idiomatic. And you should NULL intfdata.
Regards Oliver
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