Re: [PATCH] of: Split up name & type in modalias generation

[Thierry Reding]

On Fri, Sep 07, 2018 at 12:56:09PM -0700, Frank Rowand wrote:
> On 09/07/18 11:49, Rob Herring wrote:
> > On Fri, Sep 7, 2018 at 9:22 AM Thierry Reding <thierry.reding@xxxxxxxxx> wrote:
> >>
> >> From: Thierry Reding <treding@xxxxxxxxxx>
> >>
> >> The kernel's vsnprintf() implementation discards all alpha-numeric
> >> characters following a %p conversion specifier. This is done in order to
> >> generically skip any of the various modifiers that the kernel supports.
> >> Unfortunately, the OF modalias is generated with a format string that
> >> violates the assumption made by vsnprintf():
> >>
> >>         of:N%pOFnT%s
> >>
> >> While processing the above format string, vsnprintf() will eat the 'T'
> >> character, assuming that it belongs to the preceeding %p specifier. This
> >> results in a modalias with an incompatible format, which in turn causes
> >> the automatic loading of drivers based on modalias to no longer work.
> >>
> >> To fix this, split up the generation of the name & type fields into two
> >> separate snprintf() calls to avoid confusing the parser.
> >>
> >> Fixes: 73813f8483b1 ("of: Convert to using %pOFn instead of device_node.name")
> >> Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
> >> ---
> >> Note that a more elegant fix would be to make the %p format specifier
> >> parser report back the exact number of characters consumed. I briefly
> >> tried to implement it, but quickly ran into numerous special cases
> >> that make this solution rather involved.
> >>
> >> I can spend some more time to improve this in general if that's what we
> >> ultimately want, but I think this patch is a better short-term fix to
> >> workaround the issue.
> > 
> > See my reply on the original patch. I've updated the patch in my
> > dt/next branch with the fix to use %c.
> > 
> > Rob
> > 
> 
> Agreed, your updated patch is more compact and looks cleaner.

Not sure about "cleaner", but yeah, that works as well.

Thierry

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