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    SubjectRe: [PATCH v4 08/23] ata: libahci_platform: Sanity check the DT child nodes number
    On Tue, Jun 14, 2022 at 05:23:33PM +0900, Damien Le Moal wrote:
    > On 6/10/22 17:17, Serge Semin wrote:
    > > Having greater than AHCI_MAX_PORTS (32) ports detected isn't that 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 5 bits wide and the
    > > 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@baikalelectronics.ru>
    > > Reviewed-by: Hannes Reinecke <hare@suse.de>
    > >
    > > ---
    > >
    > > Changelog v2:
    > > - Drop the else word from the child_nodes value checking if-else-if
    > > statement (@Damien) and convert the after-else part into the ternary
    > > operator-based statement.
    > >
    > > Changelog v4:
    > > - Fix some logical mistakes in the patch log. (@Sergei Shtylyov)
    > > ---
    > > drivers/ata/libahci_platform.c | 13 ++++++++++---
    > > 1 file changed, 10 insertions(+), 3 deletions(-)
    > >
    > > diff --git a/drivers/ata/libahci_platform.c b/drivers/ata/libahci_platform.c
    > > index 814804582d1d..8aed7b29c7ab 100644
    > > --- a/drivers/ata/libahci_platform.c
    > > +++ b/drivers/ata/libahci_platform.c
    > > @@ -451,15 +451,22 @@ struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev,
    > > }
    > > }
    > >
    > > - hpriv->nports = child_nodes = of_get_child_count(dev->of_node);
    > > + /*
    > > + * Too many sub-nodes most likely means having something wrong with
    > > + * the firmware.
    > > + */
    > > + child_nodes = of_get_child_count(dev->of_node);
    > > + if (child_nodes > AHCI_MAX_PORTS) {
    > > + rc = -EINVAL;
    > > + goto err_out;
    > > + }
    > >
    > > /*
    > > * If no sub-node was found, we still need to set nports to
    > > * one in order to be able to use the
    > > * ahci_platform_[en|dis]able_[phys|regulators] functions.
    > > */
    > > - if (!child_nodes)
    > > - hpriv->nports = 1;
    > > + hpriv->nports = child_nodes ?: 1;
    >

    > This change is not necessary and makes the code far less easy to read.

    elaborate please. What change? What part of this change makes the code
    less easy to read?

    -Sergey

    >
    > >
    > > hpriv->phys = devm_kcalloc(dev, hpriv->nports, sizeof(*hpriv->phys), GFP_KERNEL);
    > > if (!hpriv->phys) {
    >
    >
    > --
    > Damien Le Moal
    > Western Digital Research

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