linux-kernel - Re: [PATCH] mtd: ubi: fix NVMEM over UBI volumes on 32-bit systems

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Date: Tue, 27 Feb 2024 12:57:07 +0000
From: Daniel Golle <daniel@...rotopia.org>
To: Zhihao Cheng <chengzhihao1@...wei.com>
Cc: Richard Weinberger <richard@....at>,
	Miquel Raynal <miquel.raynal@...tlin.com>,
	Vignesh Raghavendra <vigneshr@...com>,
	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mtd: ubi: fix NVMEM over UBI volumes on 32-bit systems

On Tue, Feb 27, 2024 at 10:23:17AM +0800, Zhihao Cheng wrote:
> 在 2024/2/27 2:23, Daniel Golle 写道:
> > A compiler warning related to sizeof(int) != 8 when calling do_div()
> > is triggered when building on 32-bit platforms.
> > Address this by using integer types having a well-defined size where
> > appropriate.
> > 
> > Fixes: 3ce485803da1 ("mtd: ubi: provide NVMEM layer over UBI volumes")
> > Signed-off-by: Daniel Golle <daniel@...rotopia.org>
> > ---
> >   drivers/mtd/ubi/nvmem.c | 5 ++++-
> >   1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/mtd/ubi/nvmem.c b/drivers/mtd/ubi/nvmem.c
> > index b7a93c495d172..5820a170d2512 100644
> > --- a/drivers/mtd/ubi/nvmem.c
> > +++ b/drivers/mtd/ubi/nvmem.c
> > @@ -23,14 +23,17 @@ struct ubi_nvmem {
> >   static int ubi_nvmem_reg_read(void *priv, unsigned int from,
> >   			      void *val, size_t bytes)
> >   {
> > -	int err = 0, lnum = from, offs, bytes_left = bytes, to_read;
> > +	uint32_t bytes_left, offs, to_read;
> >   	struct ubi_nvmem *unv = priv;
> >   	struct ubi_volume_desc *desc;
> > +	uint64_t lnum = from;
> > +	int err = 0;
> >   	desc = ubi_open_volume(unv->ubi_num, unv->vol_id, UBI_READONLY);
> >   	if (IS_ERR(desc))
> >   		return PTR_ERR(desc);
> > +	bytes_left = bytes;
> The 'bytes' is a size_t type, which has 64 bits on 64-bit platforms. This
> assignment will lead a type truncation, so should we add a explicit type
> conversion here to avoid compiler warning?

Oh right. I reckon the best is to declare 'bytes' as 'size_t' type as well
then. I will send v2 with that change shortly.

> >   	offs = do_div(lnum, unv->usable_leb_size);
> >   	while (bytes_left) {
> >   		to_read = unv->usable_leb_size - offs;
> > 
> 
> 
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/

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