linux-kernel - Re: [PATCH 1/1] pps: clients: gpio: Bypass edge's direction check when not needed

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <28c5456d-535c-4ed9-b13a-fab7f50412be@bootlin.com>
Date: Thu, 11 Apr 2024 14:44:44 +0200
From: Bastien Curutchet <bastien.curutchet@...tlin.com>
To: Rodolfo Giometti <giometti@...eenne.com>
Cc: linux-kernel@...r.kernel.org,
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, herve.codina@...tlin.com,
 christophercordahi@...ometrics.ca
Subject: Re: [PATCH 1/1] pps: clients: gpio: Bypass edge's direction check
 when not needed

Hi Rodolfo

>>> diff --git a/drivers/pps/clients/pps-gpio.c 
>>> b/drivers/pps/clients/pps-gpio.c
>>> index 2f4b11b4dfcd..f05fb15ed7f4 100644
>>> --- a/drivers/pps/clients/pps-gpio.c
>>> +++ b/drivers/pps/clients/pps-gpio.c
>>> @@ -52,7 +52,9 @@ static irqreturn_t pps_gpio_irq_handler(int irq, 
>>> void *data)
>>>
>>>          info = data;
>>>
>>> -       rising_edge = gpiod_get_value(info->gpio_pin);
>>> +       rising_edge = info->capture_clear ? \
>>> +                       gpiod_get_value(info->gpio_pin) : \
>>> +                       !info->assert_falling_edge;
>>>          if ((rising_edge && !info->assert_falling_edge) ||
>>>                          (!rising_edge && info->assert_falling_edge))
>>>                  pps_event(info->pps, &ts, PPS_CAPTUREASSERT, data);
>>>
>>> Please, review and test it before resubmitting. :)
>>>
>>
>> I'll try this and send a V2 after my tests, thank you.
> 
> OK, thanks.
> 
> However we should think very well about this modification since it could 
> be the case where we have a device sending both assert and clear events 
> but we wish to catch just the asserts... in this case we will get 
> doubled asserts!
> 

My understanding is that clear events are to be captured only when this
capture_clear boolean is set. If it is not set, the PPS_CAPTURECLEAR
flag is not added to pps_source_info->mode and get_irqf_trigger_flags()
will return only one edge flag (rising or falling depending on
assert-falling-edge DT property).

By the way, I see that the capture_clear is never set since the legacy
platform data support has been dropped (commit ee89646619ba).


Best regards,
Bastien