linux-kernel - Re: [PATCH] mmc: part_switch: fixes switch on gp3 partition

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Message-ID: <CAPDyKFqYDPgNjSkpH=XATkUY2XtjsaDstChcAnGxoas4jgDVfw@mail.gmail.com>
Date: Wed, 6 Mar 2024 16:56:26 +0100
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Linus Walleij <linus.walleij@...aro.org>
Cc: "Jorge Ramirez-Ortiz, Foundries" <jorge@...ndries.io>, Jens Wiklander <jens.wiklander@...aro.org>, 
	Tomas Winkler <tomas.winkler@...el.com>, Dominique Martinet <asmadeus@...ewreck.org>, 
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Dominique Martinet <dominique.martinet@...ark-techno.com>, stable@...r.kernel.org
Subject: Re: [PATCH] mmc: part_switch: fixes switch on gp3 partition

On Wed, 6 Mar 2024 at 15:38, Linus Walleij <linus.walleij@...aro.org> wrote:
>
> On Wed, Mar 6, 2024 at 3:22 PM Jorge Ramirez-Ortiz, Foundries
> <jorge@...ndries.io> wrote:
>
> > I still cant grasp how "target_part = idata->rpmb->part_index" is
> > helping in the design.
> >
> > What happens when:
> > 1) EXT_CSD_PART_CONFIG_ACC_MASK > part_index > EXT_CSD_PART_CONFIG_ACC_RPMB
> > target_part now could be indicating a GP instead of an RPMB leading to failures.
> >
> > 2) part_index <= EXT_CSD_PART_CONFIG_ACC_RPMB
> > loses the part_index value .
> >
> > So part_index should be larger than EXT_CSD_PART_CONFIG_ACC_MASK even
> > though the comment indicates it starts at 0?
> >
> > /**
> >  * struct mmc_rpmb_data - special RPMB device type for these areas
> >  * @dev: the device for the RPMB area
> >  * @chrdev: character device for the RPMB area
> >  * @id: unique device ID number
> >  * @part_index: partition index (0 on first)    <---------------------
> >  * @md: parent MMC block device
> >  * @node: list item, so we can put this device on a list
> >  */
> > struct mmc_rpmb_data {
> >         struct device dev;
> >         struct cdev chrdev;
> >         int id;
> >
> > is it just possible that "target_part = idata->rpmb->part_index" just
> > needs to be shifted to avoid issues?
> >
> > I think the fix to the regression I introduced could perhaps address
> > this as well.
>
> I have no clue how the regression happened really ... heh.
>
> We should probably rename it part_cfg because that is what we
> store in it, it's assigned from card->part[idx].part_cfg.
>
> Then the id field in mmc_rpmb_data should be deleted along
> with all the IDA counter code etc and the partition name hardcoded
> to be "0" as there will never be anything else.

Seems reasonable to me. Are you thinking of sending a cleanup patch on
top of $subject patch?

Kind regards
Uffe