linux-kernel - Re: uio: add the uio

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Message-ID: <20090121170116.GA18567@jenkins.ifup.org>
Date:	Wed, 21 Jan 2009 09:01:16 -0800
From:	Brandon Philips <brandon@...p.org>
To:	"Hans J. Koch" <hjk@...utronix.de>
Cc:	Greg KH <gregkh@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: uio: add the uio_aec driver

On 22:48 Tue 20 Jan 2009, Hans J. Koch wrote:
> On Tue, Jan 20, 2009 at 12:47:29PM -0800, Brandon Philips wrote:
> > UIO driver for the Adrienne Electronics Corporation PCI time code
> > device.
> > 
> > This device differs from other UIO devices since it uses I/O ports instead of
> > memory mapped I/O. In order to make it possible for UIO to work with this
> > device a utility, uioport, can be used to read and write the ports.
> 
> We just added a feature to UIO that allows you to pass information about
> such I/O ports to userspace. In struct uio_info, there's now also a port[]
> array for that purpose. In your case, you will probably want to set the
> the porttype member of struct uio_port to UIO_PORT_X86.
> 
> The portio feature is available since .29-rc1, please use it.

Sounds good. I will rework it along with your suggestions below.

> > uioport is designed to be a setuid program and checks the permissions of
> > the /dev/uio* node and if the user has write permissions it will use
> > iopl and out*/in* to access the device.
> 
> What happens with PCI on PowerPC ?

I don't know. I could use /dev/port but my concern is that the device
spec sheet specifies that some writes should be done with outb and
others with outl. /dev/port only uses outb. Do you know if outl is
different than four outb's to a device?

Cheers,

	Brandon

> > @@ -91,5 +91,6 @@ extern void uio_event_notify(struct uio_
> >  #define UIO_MEM_PHYS	1
> >  #define UIO_MEM_LOGICAL	2
> >  #define UIO_MEM_VIRTUAL 3
> > +#define UIO_MEM_PORT	4
> 
> As I explained above, this is not needed anymore. The reason we don't want
> this: It breaks generic userspace tools that rely on the fact that any
> memory found underneath the maps/ directory in sysfs can be mapped.
> 
> In case of ports we don't have anything to be mapped, we simply want to
> pass information to userspace. That justifies having a different sysfs
> directory for it.

ack.

> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/pci.h>
> > +#include <linux/init.h>
> > +#include <linux/interrupt.h>
> > +#include <linux/cdev.h>
> > +#include <linux/fs.h>
> > +#include <linux/io.h>
> > +#include <asm/system.h>
> 
> please put this <asm/...> include under the <linux/...> includes, separated by
> one blank line. Makes it easier to find. BTW, do you actually need this one?

ack.

> > +	iowrite32(INT_ENABLE, info->mem[0].internal_addr + INT_ENABLE_ADDR);
> > +	iowrite8(INT_MASK_ALL, info->mem[0].internal_addr + INT_MASK_ADDR);
> > +	if (ioread8(info->mem[0].internal_addr + INTA_DRVR_ADDR)
> > +			& INTA_ENABLED_FLAG)
> > +		printk(KERN_INFO "aectc: interrupts successfully enabled\n");
> 
> I'd find it better if you printed a message in case of failure...
> And please use dev_err() etc. instead of printk().

ack.

> BTW, if this test fails, are you sure you can continue and let probe()
> succeed?

Yes, if it fails the device still has a "polling" mode.
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