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From:   Richard Weinberger <richard.weinberger@gmail.com>
Date:   Wed, 22 May 2019 23:35:18 +0200
Message-ID: <CAFLxGvxGCKi1HH_7tit4ykQDJGm9t6Gt8pz7LTCZZ8G4J8sOhw@mail.gmail.com>
Subject: Re: [PATCH 2/2] mtd: concat: implement _is_locked mtd operation
To:     Chris Packham <Chris.Packham@alliedtelesis.co.nz>
Cc:     David Woodhouse <dwmw2@infradead.org>,
        Brian Norris <computersforpeace@gmail.com>,
        Marek Vasut <marek.vasut@gmail.com>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        "linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Wed, May 22, 2019 at 11:26 PM Richard Weinberger
<richard.weinberger@gmail.com> wrote:
>
> On Wed, May 22, 2019 at 11:06 PM Chris Packham
> <Chris.Packham@alliedtelesis.co.nz> wrote:
> >
> > On 23/05/19 8:44 AM, Richard Weinberger wrote:
> > > On Wed, May 22, 2019 at 2:08 AM Chris Packham
> > > <chris.packham@alliedtelesis.co.nz> wrote:
> > >>
> > >> Add an implementation of the _is_locked operation for concatenated mtd
> > >> devices. As with concat_lock/concat_unlock this can simply use the
> > >> common helper and pass mtd_is_locked as the operation.
> > >>
> > >> Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
> > >> ---
> > >>   drivers/mtd/mtdconcat.c | 6 ++++++
> > >>   1 file changed, 6 insertions(+)
> > >>
> > >> diff --git a/drivers/mtd/mtdconcat.c b/drivers/mtd/mtdconcat.c
> > >> index 9514cd2db63c..0e919f3423af 100644
> > >> --- a/drivers/mtd/mtdconcat.c
> > >> +++ b/drivers/mtd/mtdconcat.c
> > >> @@ -496,6 +496,11 @@ static int concat_unlock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
> > >>          return __concat_xxlock(mtd, ofs, len, mtd_unlock);
> > >>   }
> > >>
> > >> +static int concat_is_locked(struct mtd_info *mtd, loff_t ofs, uint64_t len)
> > >> +{
> > >> +       return __concat_xxlock(mtd, ofs, len, mtd_is_locked);
> > >> +}
> > >
> > > Hmm, here you start abusing your own new API. :(
> >
> > Abusing because xxlock is a poor choice of name? I initially had a third
> > copy of the logic from lock/unlock which is what lead me to do the
> > cleanup first. mtd_lock(), mtd_unlock() and mtd_is_locked() all work the
> > same way namely given an offset and a length either lock, unlock or
> > return the status of the len/erasesz blocks at ofs.
>
> Well, for unlock/lock it is just a loop which applies an operation to
> a given range on all submtds.
> But as soon an operation returns non-zero, the loop stops and returns
> that error.
> This makes sense for unlock/lock.
>
> Now you abuse this as "apply a random mtd operation to a given range".
> So, giving it a proper name is the first step. Step two is figuring
> for what kind
> of mtd operations it makes sense and is correct.
>
> > >
> > > Did you verify that the unlock/lock-functions deal correctly with all
> > > semantics from mtd_is_locked?
> > > i.e. mtd_is_locked() with len = 0 returns 1 for spi-nor.
> > >
> >
> > I believe so. I've only got access to a parallel NOR flash system that
> > uses concatenation and that seems sane  (is mtdconcat able to work with
> > spi memories?). The concat_is_locked() should just reflect what the
> > underlying mtd device driver returns.
>
> mtdconcat *should* work with any mtd. But I never used it much, I see
> it more as legacy
> code.
>
> What happens if one submtd is locked and another not?
> Does concat_is_locked() return something sane then?
> I'd expect it to return true if at least one submtd is locked and 0
> of no submtd is locked.

BTW: Meant overlapping requests. If it targets always only one submtd,
it is easy.

-- 
Thanks,
//richard