linux-kernel - Re: [PATCH v3 09/23] ata: libahci_platform: Sanity check the DT child nodes number

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Date:   Thu, 12 May 2022 11:24:22 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...il.com>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>,
        Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Jens Axboe <axboe@...nel.dk>
Cc:     Serge Semin <fancer.lancer@...il.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Rob Herring <robh+dt@...nel.org>, linux-ide@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v3 09/23] ata: libahci_platform: Sanity check the DT child
 nodes number

On 5/12/22 2:17 AM, Serge Semin wrote:

> Having greater than (AHCI_MAX_PORTS = 32) ports detected isn't that

   Having greater than AHCI_MAX_PORTS (32) ports detected?

> critical from the further AHCI-platform initialization point of view since
> exceeding the ports upper limit will cause allocating more resources than
> will be used afterwards. But detecting too many child DT-nodes doesn't
> seem right since it's very unlikely to have it on an ordinary platform. In
> accordance with the AHCI specification there can't be more than 32 ports
> implemented at least due to having the CAP.NP field of 4 bits wide and the

   It's 5 bits wide, actually...

> PI register of dword size. Thus if such situation is found the DTB must
> have been corrupted and the data read from it shouldn't be reliable. Let's
> consider that as an erroneous situation and halt further resources
> allocation.
> 
> Note it's logically more correct to have the nports set only after the
> initialization value is checked for being sane. So while at it let's make
> sure nports is assigned with a correct value.
> 
> Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>

[...]

MBR, Sergey