linux-kernel - Re: [PATCH 2/6] staging: ft1000: Use misc device instead self created device.

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Message-ID: <20101129194414.GB14086@kroah.com>
Date:	Mon, 29 Nov 2010 11:44:14 -0800
From:	Greg KH <greg@...ah.com>
To:	Belisko Marek <marek.belisko@...il.com>
Cc:	Jiri Slaby <jirislaby@...il.com>, devel@...verdev.osuosl.org,
	Greg Kroah-Hartman <gregkh@...e.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/6] staging: ft1000: Use misc device instead self
 created device.

On Wed, Nov 24, 2010 at 10:16:36AM +0100, Belisko Marek wrote:
> On Tue, Nov 23, 2010 at 10:28 PM, Jiri Slaby <jirislaby@...il.com> wrote:
> > On 11/23/2010 03:00 PM, Belisko Marek wrote:
> >> On Tue, Nov 23, 2010 at 2:53 PM, Jiri Slaby <jirislaby@...il.com> wrote:
> >>> On 11/23/2010 01:29 PM, Marek Belisko wrote:
> >>>> Use simple misc device for ioctl driver funtionality testing.
> >>>>
> >>>> Signed-off-by: Marek Belisko <marek.belisko@...n-nandra.com>
> >>>> ---
> >>>>  drivers/staging/ft1000/ft1000-usb/ft1000_chdev.c |   90 ++++++++++++++++++---
> >>>>  1 files changed, 77 insertions(+), 13 deletions(-)
> >>>>
> >>>> diff --git a/drivers/staging/ft1000/ft1000-usb/ft1000_chdev.c b/drivers/staging/ft1000/ft1000-usb/ft1000_chdev.c
> >>>> index 1aec926..d1784a3 100644
> >>>> --- a/drivers/staging/ft1000/ft1000-usb/ft1000_chdev.c
> >>>> +++ b/drivers/staging/ft1000/ft1000-usb/ft1000_chdev.c
> >>>> @@ -32,6 +32,7 @@
> >>>>  #include <linux/poll.h>
> >>>>  #include <linux/netdevice.h>
> >>>>  #include <linux/delay.h>
> >>>> +#include <linux/miscdevice.h>
> >>>>
> >>>>  #include <linux/fs.h>
> >>>>  #include <linux/kmod.h>
> >>>> @@ -78,6 +79,47 @@ static struct file_operations ft1000fops =
> >>>>       .llseek         = no_llseek,
> >>>>  };
> >>>>
> >>>> +struct ft1000_misc_device {
> >>>> +     struct miscdevice dev;
> >>>> +     int inf_id;
> >>>> +};
> >>>> +
> >>>> +#define FREE_ID (0xFF)
> >>>> +
> >>>> +/* we support just 3 devices */
> >>>> +#define MAX_DEVICE 3
> >>>
> >>> No, why this should be converted to miscdevice? Leave it as chrdev.
> >> Is there any problem with using miscdev?
> >
> > Yes, if you want more than a single device per system.
> >
> >> Old interface create /dev nodes with
> >> calling kernel thread and some usermode_helper or whatever.
> >
> > Yes, that's crap indeed. But doesn't judge for miscdevice.
> >
> >> Just convert to misc dev
> >> where this is done automatically.
> >
> > So the only thing you need to do is to send a uevent to udev appropriately.
> Could be used something like:
> register_chrdev(0,"ft1000", &fops)
> class = class_create(THIS_MODULE, "ft1000");
> device_create(class, NULL, MKDEV(major, i), NULL, "ft1000%d", i);
> Then will be created different devices for every plugged device.
> This should have effect of automatic device node creation also suppose.

Please don't create new classes.

Is this a USB device?  If so, why not just use the USB major number?
Just ask me and I can reserve you a USB minor number for your driver.

thanks,

greg k-h
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