linux-kernel - Re: [PATCH 05/11] RISC-V: drivers/iommu/riscv: Add sysfs interface

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Message-ID: <CAH2o1u6pMF3MN=oFBcs9kOf-nwnEYfD2Vv=89+DzUanV59R5dw@mail.gmail.com>
Date:   Thu, 20 Jul 2023 11:30:03 -0700
From:   Tomasz Jeznach <tjeznach@...osinc.com>
To:     Krzysztof Kozlowski <krzk@...nel.org>
Cc:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Anup Patel <apatel@...tanamicro.com>,
        Sunil V L <sunilvl@...tanamicro.com>,
        Nick Kossifidis <mick@....forth.gr>,
        Sebastien Boeuf <seb@...osinc.com>, iommu@...ts.linux.dev,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux@...osinc.com
Subject: Re: [PATCH 05/11] RISC-V: drivers/iommu/riscv: Add sysfs interface

On Wed, Jul 19, 2023 at 11:38 PM Krzysztof Kozlowski <krzk@...nel.org> wrote:
>
> On 19/07/2023 21:33, Tomasz Jeznach wrote:
> > Enable sysfs debug / visibility interface providing restricted
> > access to hardware registers.
>
> Please use subject prefixes matching the subsystem. You can get them for
> example with `git log --oneline -- DIRECTORY_OR_FILE` on the directory
> your patch is touching.
>

ack.

> >
> > Signed-off-by: Tomasz Jeznach <tjeznach@...osinc.com>
> > ---
> >  drivers/iommu/riscv/Makefile      |   2 +-
> >  drivers/iommu/riscv/iommu-sysfs.c | 183 ++++++++++++++++++++++++++++++
> >  drivers/iommu/riscv/iommu.c       |   7 ++
> >  drivers/iommu/riscv/iommu.h       |   2 +
> >  4 files changed, 193 insertions(+), 1 deletion(-)
> >  create mode 100644 drivers/iommu/riscv/iommu-sysfs.c
> >
> > diff --git a/drivers/iommu/riscv/Makefile b/drivers/iommu/riscv/Makefile
> > index 38730c11e4a8..9523eb053cfc 100644
> > --- a/drivers/iommu/riscv/Makefile
> > +++ b/drivers/iommu/riscv/Makefile
> > @@ -1 +1 @@
> > -obj-$(CONFIG_RISCV_IOMMU) += iommu.o iommu-pci.o iommu-platform.o
> > \ No newline at end of file
> > +obj-$(CONFIG_RISCV_IOMMU) += iommu.o iommu-pci.o iommu-platform.o iommu-sysfs.o
> > \ No newline at end of file
>
> You have this error in multiple places.
>

ack. next version will run through checkpatch.pl, should spot such problems.

> > diff --git a/drivers/iommu/riscv/iommu-sysfs.c b/drivers/iommu/riscv/iommu-sysfs.c
> > new file mode 100644
> > index 000000000000..f038ea8445c5
> > --- /dev/null
> > +++ b/drivers/iommu/riscv/iommu-sysfs.c
> > @@ -0,0 +1,183 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * IOMMU API for RISC-V architected Ziommu implementations.
> > + *
> > + * Copyright © 2022-2023 Rivos Inc.
> > + *
> > + * Author: Tomasz Jeznach <tjeznach@...osinc.com>
> > + */
> > +
> > +#include <linux/module.h>
> > +#include <linux/kernel.h>
> > +#include <linux/compiler.h>
> > +#include <linux/iommu.h>
> > +#include <linux/platform_device.h>
> > +#include <asm/page.h>
> > +
> > +#include "iommu.h"
> > +
> > +#define sysfs_dev_to_iommu(dev) \
> > +     container_of(dev_get_drvdata(dev), struct riscv_iommu_device, iommu)
> > +
> > +static ssize_t address_show(struct device *dev,
> > +                         struct device_attribute *attr, char *buf)
>
>
> Where is the sysfs ABI documented?
>

Sysfs for now is used only to expose selected IOMMU memory mapped
registers, with complete documentation in the RISC-V IOMMU Arch Spec
[1], and some comments in iommu-bits.h file.
LMK If it would be better to put a dedicated file documenting those
with the patch itself.


[1] https://github.com/riscv-non-isa/riscv-iommu/releases/download/v1.0/riscv-iommu.pdf

>
> Best regards,
> Krzysztof
>

regards,
- Tomasz