linux-kernel - Re: [PATCH 3/3] firmware: fw_cfg: create directory hierarchy for fw

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Message-ID: <20150810183245.GB18817@kroah.com>
Date:	Mon, 10 Aug 2015 11:32:45 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	"Gabriel L. Somlo" <somlo@....edu>
Cc:	ralf@...ux-mips.org, zajec5@...il.com, paul@...an.com,
	galak@...eaurora.org, linux-api@...r.kernel.org,
	linux-kernel@...r.kernel.org, matt.fleming@...el.com,
	x86@...nel.org, linux-efi@...r.kernel.org, qemu-devel@...gnu.org,
	lersek@...hat.com, jordan.l.justen@...el.com,
	gleb@...udius-systems.com, pbonzini@...hat.com, kraxel@...hat.com,
	eblake@...hat.com, rjones@...hat.com,
	kernelnewbies@...nelnewbies.org
Subject: Re: [PATCH 3/3] firmware: fw_cfg: create directory hierarchy for
 fw_cfg file names

On Mon, Aug 10, 2015 at 12:31:20PM -0400, Gabriel L. Somlo wrote:
> From: "Gabriel Somlo" <somlo@....edu>
> 
> Each fw_cfg entry of type "file" has an associated 56-char,
> nul-terminated ASCII string which represents its name. While
> the fw_cfg device doesn't itself impose any specific naming
> convention, QEMU developers have traditionally used path name
> semantics (i.e. "etc/acpi/rsdp") to descriptively name the
> various fw_cfg "blobs" passed into the guest.
> 
> This patch attempts, on a best effort basis, to create a
> directory hierarchy representing the content of fw_cfg file
> names, under /sys/firmware/fw_cfg/by_name.
> 
> Upon successful creation of all directories representing the
> "dirname" portion of a fw_cfg file, a symlink will be created
> to represent the "basename", pointing at the appropriate
> /sys/firmware/fw_cfg/by_select entry. If a file name is not
> suitable for this procedure (e.g., if its basename or dirname
> components collide with an already existing dirname component
> or basename, respectively) the corresponding fw_cfg blob is
> skipped and will remain available in sysfs only by its selector
> key value.

Shouldn't all of this be done in userspace with the symlinks and all?
It seems like you are trying to duplicate the /dev/block/by-name and
such.  Policy decisions like symlinks and naming should be done there,
in userspace, and not directly in sysfs if at all possible.

Again, why can't this be a bunch of character device nodes?  It seems
like you want to access them that way (read/write, ioctl, etc.)

thanks,

greg k-h
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