Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Feedback-ID: i56a14606:Fastmail
User-Agent: Cyrus-JMAP/3.9.0-alpha0-238-g746678b8b6-fm-20230329.001-g746678b8
Mime-Version: 1.0
Message-Id: <242a5400-b5e6-4707-af88-1d695e114f78@app.fastmail.com>
In-Reply-To: <20230330114242.GC434339@google.com>
References: <20230320152319.665592-1-loic.poulain@linaro.org>
 <20230330114242.GC434339@google.com>
Date:   Thu, 30 Mar 2023 14:45:18 +0200
From:   "Arnd Bergmann" <arnd@arndb.de>
To:     "Lee Jones" <lee@kernel.org>,
        "Loic Poulain" <loic.poulain@linaro.org>
Cc:     linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mfd: syscon: Use of_io_request_and_map() for IO mapping
Content-Type: text/plain
Precedence: bulk

On Thu, Mar 30, 2023, at 13:42, Lee Jones wrote:
> On Mon, 20 Mar 2023, Loic Poulain wrote:
>
>> Use of_io_request_and_map() instead of of_iomap() so that the
>> region is reserved and protected, i.e reported in /proc/iomem
>> and not accessible from user side (CONFIG_IO_STRICT_DEVMEM).
>>
>> Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
>> ---
>>  drivers/mfd/syscon.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
>> index bdb2ce7ff03b..7e6d4edda118 100644
>> --- a/drivers/mfd/syscon.c
>> +++ b/drivers/mfd/syscon.c
>> @@ -60,7 +60,7 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_clk)
>>  		goto err_map;
>>  	}
>>
>> -	base = of_iomap(np, 0);
>> +	base = of_io_request_and_map(np, 0, NULL);
>>  	if (!base) {
>>  		ret = -ENOMEM;
>>  		goto err_map;
>
> Looks sane though.
>
> Arnd, do you have an opinion?

Thanks for pinging me. I would indeed expect this to cause
problems, as syscon mappings are likely to be used in a way
that is not entirely clean, with other devices defining
overlapping ranges.

For any other driver, the change makes a lot of sense after
checking the DT file, but for syscon in particular I don't
think it's even realistic to check all users.

     Arnd