Re: [PATCH] driver-core: devtmpfs - driver core maintained /dev tmpfs

Greg KH
2009-05-01T06:17:41Z

On Thu, Apr 30, 2009 at 10:29:00PM -0700, Andrew Morton wrote:
> On Thu, 30 Apr 2009 15:23:42 +0200 Kay Sievers <kay.sievers@vrfy.org> wrote:
>
> > From: Kay Sievers <kay.sievers@vrfy.org>
> > Subject: driver-core: devtmpfs - driver core maintained /dev tmpfs
> >
> > Devtmpfs lets the kernel create a tmpfs very early at kernel
> > initialization, before any driver core device is registered. Every
> > device with a major/minor will have a device node created in this
> > tmpfs instance. After the rootfs is mounted by the kernel, the
> > populated tmpfs is mounted at /dev. In initramfs, it can be moved
> > to the manually mounted root filesystem before /sbin/init is
> > executed.
>
> Lol, devfs.

Well, devfs "done right" with hopefully none of the vfs problems the
last devfs had. :)

> > block/bsg.c | 6
> > drivers/gpu/drm/drm_sysfs.c | 7
> > drivers/input/input.c | 6
> > drivers/media/dvb/dvb-core/dvbdev.c | 10 +
> > drivers/usb/core/usb.c | 11 +
>
> These five subsystems were updated, but there are so many others. Why
> these five in particular?

These are the ones that create a subdirectory in /dev/ None of the
others do.

> > +const char *device_get_nodename(struct device *dev, const char **tmp)
> > +{
> > + char *s;
> > +
> > + *tmp = NULL;
> > +
> > + /* the device type may provide a specific name */
> > + if (dev->type && dev->type->nodename)
> > + *tmp = dev->type->nodename(dev);
>
> dev->type->nodename() might have failed due to -ENOMEM, in which case
> it seems wrong to assume that it returned NULL for <whatever reason you
> thought it might want to return NULL>.
>
> It's all a bit confused.

I'll let Kay answer this one.

> > + if (*tmp)
> > + return *tmp;
> > +
> > + /* the class may provide a specific name */
> > + if (dev->class && dev->class->nodename)
> > + *tmp = dev->class->nodename(dev);
> > + if (*tmp)
> > + return *tmp;
> > +
> > + /* return name without allocation, tmp == NULL */
> > + if (strchr(dev_name(dev), '!') == NULL)
>
> s/ / /

good catch. I've edited that in the version of this patch in my tree.

thanks,

greg k-h