linux-kernel - Re: [PATCH v3] dmi: Make dmi_walk and dmi_walk

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Message-ID: <20160130180517.GB1862@malice.jf.intel.com>
Date:	Sat, 30 Jan 2016 10:05:17 -0800
From:	Darren Hart <dvhart@...radead.org>
To:	Jean Delvare <jdelvare@...e.de>
Cc:	Andy Lutomirski <luto@...nel.org>,
	Pali Rohár <pali.rohar@...il.com>,
	platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] dmi: Make dmi_walk and dmi_walk_early return real
 error codes

On Fri, Jan 22, 2016 at 10:12:22AM +0100, Jean Delvare wrote:
> Hi Andy,
> 
> Sorry for the delay.
> 
> On Tue, 19 Jan 2016 15:54:46 -0800, Andy Lutomirski wrote:
> > Currently they return -1 on error, which will confuse callers if
> > they try to interpret it as a normal negative error code.
> > 
> > Signed-off-by: Andy Lutomirski <luto@...nel.org>
> > ---
> > 
> > Changes from v3:
> 
> You mean from v2...
> 
> >  - Split out from the series it was in.
> >  - Use -ENXIO for "there's no DMI".
> >  - Also fix docs and !DMI case.
> > 
> > Changes from v2:
> 
> ... and from v1.
> 
> >  - Total rewrite.
> > 
> > drivers/firmware/dmi_scan.c | 9 +++++----
> >  include/linux/dmi.h         | 2 +-
> >  2 files changed, 6 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
> > index 0e08e665f715..0418fed261bb 100644
> > --- a/drivers/firmware/dmi_scan.c
> > +++ b/drivers/firmware/dmi_scan.c
> > @@ -144,7 +144,7 @@ static int __init dmi_walk_early(void (*decode)(const struct dmi_header *,
> >  
> >  	buf = dmi_early_remap(dmi_base, orig_dmi_len);
> >  	if (buf == NULL)
> > -		return -1;
> > +		return -ENOMEM;
> >  
> >  	dmi_decode_table(buf, decode, NULL);
> >  
> > @@ -970,7 +970,8 @@ EXPORT_SYMBOL(dmi_get_date);
> >   *	@decode: Callback function
> >   *	@private_data: Private data to be passed to the callback function
> >   *
> > - *	Returns -1 when the DMI table can't be reached, 0 on success.
> > + *	Returns 0 on success, -ENXIO if DMI is not selected or not present,
> > + *	or a different negative error code if DMI walking fails.
> 
> Returning an error from DMI walking isn't yet implemented so this is
> confusing. If it ever is, most likely it will be implemented as a
> separate function. Or were you only referring to the -ENOMEM case below?
> 
> >   */
> >  int dmi_walk(void (*decode)(const struct dmi_header *, void *),
> >  	     void *private_data)
> > @@ -978,11 +979,11 @@ int dmi_walk(void (*decode)(const struct dmi_header *, void *),
> >  	u8 *buf;
> >  
> >  	if (!dmi_available)
> > -		return -1;
> > +		return -ENOENT;
> 
> Should be -ENXIO as documented above? Not that I really understand how
> "No such device or address" is going to be a helpful error message for
> the user. What's wrong with -ENOTSUP I suggested earlier?
> 

Andy,

If I understand this correctly, this is the first of 5 patches, and this one has
some unanswered questions from Jean here. If this patch gets respun, the
following are also impacted:

dell-wmi: Stop storing pointers to DMI tables
dell-wmi, dell-laptop: select DMI
dell-wmi: Clean up hotkey table size check
dell-wmi: Support new hotkeys on the XPS 13 9350 (Skylake)

Is that correct?

If so, please close on this patch with Jean, and resend the series of 5 together
and be sure to include me on Cc.

Thanks,

-- 
Darren Hart
Intel Open Source Technology Center