From mboxrd@z Thu Jan  1 00:00:00 1970
From: Miquel Raynal <miquel.raynal@bootlin.com>
Date: Thu, 12 Jul 2018 15:12:37 +0200
Subject: [U-Boot] [PATCH v2 20/21] cmd: mtd: add 'mtd' command
In-Reply-To: <20180712145132.0d22dcce@xps13>
References: <20180711152529.24547-1-miquel.raynal@bootlin.com>
 <20180711152529.24547-21-miquel.raynal@bootlin.com>
 <20180712004213.71286527@bbrezillon>
 <20180712145132.0d22dcce@xps13>
Message-ID: <20180712151237.596453b1@xps13>
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To: u-boot@lists.denx.de

Hi Boris,

> > > +
> > > +		if (full_erase) {
> > > +			off =3D 0;
> > > +			len =3D mtd->size;
> > > +		}
> > > +
> > > +		if ((u32)off % mtd->erasesize) {   =20
> >=20
> > Sounds dangerous. We have 8GB NANDs on sunxi platforms... =20
>=20
> [...]
>=20
> > > +
> > > +		if ((u32)len % mtd->erasesize) {   =20
> >=20
> > Same here. I guess there's a do_div() in uboot. =20
>=20
> In both cases I take the less significant bytes of a 64-bit value. The
> modulo operation is safe as long as mtd->erasesize is a 32-bit value
> too. I don't think there is any danger?

As discussed out of this thread, this works because mtd->erasesize is
always a power of 2. Erase sizes not being a power of 2 do not exist
but it will be safer to switch to do_div().

Thanks,
Miqu=C3=A8l