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charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-ide@vger.kernel.org On 6/18/22 05:18, Serge Semin wrote: > On Thu, Jun 16, 2022 at 09:25:48AM +0900, Damien Le Moal wrote: >> On 2022/06/16 5:53, Serge Semin wrote: >>> 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 >>>>> Reviewed-by: Hannes Reinecke >>>>> >>>>> --- >>>>> >>>>> 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? >> > >> You changed: >> >> if (!child_nodes) >> hpriv->nports = 1; >> >> to: >> >> hpriv->nports = child_nodes ?: 1; >> >> That is the same. So the change is not needed in the first place, and worse, >> makes the code way harder to read for no good reason. > > No, they aren't the same: > + if (!child_nodes) > + hpriv->nports = 1; > and > + hpriv->nports = child_nodes ?: 1; > aren't equivalent. The equivalent implementation would be: > + if (child_nodes) > + hpriv->nports = child_nodes; > + else > + hpriv->nports = 1; Then use this code. That cryptic C code is hard to read. > > As I said in the patchlog, hpriv->nports is updated now only if > of_get_child_count() returns a valid number of the child nodes, > ports, which semantically is more correct. In the previous > implementation it was always set to the number of child nodes > no matter whether that value was correct or not. > > Regarding the ternary operator with omitted operand. Well, it's not > that rare beast in the kernel: > $ grep -r "?:" kernel/ drivers/ mm/ fs/ block/ | wc -l > 699 > But if you insist in it being not that readable, I can replace it with > more bulky if-else statement. Do you? Yes please, use the spelled out if/else. I prefer easy to read code rather than loosing time trying to understand that cryptic C syntax, which I actually did not know about. > > -Sergey > >> >>> >>> -Sergey >>> >>>> >>>>> >>>>> hpriv->phys = devm_kcalloc(dev, hpriv->nports, sizeof(*hpriv->phys), GFP_KERNEL); >>>>> if (!hpriv->phys) { >>>> >>>> >>>> -- >>>> Damien Le Moal >>>> Western Digital Research >> >> >> -- >> Damien Le Moal >> Western Digital Research -- Damien Le Moal Western Digital Research