linux-kernel - Re: [PATCH] usb: typec: tcpm: Export partner Source Capabilities

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Message-ID: <c838e214-4888-c708-6a7c-a8de6ecb5282@roeck-us.net>
Date:   Tue, 12 Feb 2019 08:19:56 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Greg KH <gregkh@...uxfoundation.org>, Kyle Tso <kyletso@...gle.com>
Cc:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Badhri Jagan Sridharan <badhri@...gle.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: typec: tcpm: Export partner Source Capabilities

On 2/12/19 2:54 AM, Greg KH wrote:
> On Tue, Feb 12, 2019 at 06:29:39PM +0800, Kyle Tso wrote:
>> On Thu, Jan 31, 2019 at 3:02 PM Greg KH <gregkh@...uxfoundation.org> wrote:
>>
>>> On Thu, Jan 31, 2019 at 11:54:11AM +0800, Kyle Tso wrote:
>>>> Provide a function to get the partner Source Capabilities.
>>>>
>>>> Signed-off-by: Kyle Tso <kyletso@...gle.com>
>>>> ---
>>>>   drivers/usb/typec/tcpm/tcpm.c | 23 +++++++++++++++++++++++
>>>>   include/linux/usb/tcpm.h      |  1 +
>>>>   2 files changed, 24 insertions(+)
>>>>
>>>> diff --git a/drivers/usb/typec/tcpm/tcpm.c
>>> b/drivers/usb/typec/tcpm/tcpm.c
>>>> index f1d3e54210df..29cd84ba9960 100644
>>>> --- a/drivers/usb/typec/tcpm/tcpm.c
>>>> +++ b/drivers/usb/typec/tcpm/tcpm.c
>>>> @@ -4494,6 +4494,29 @@ int tcpm_update_sink_capabilities(struct
>>> tcpm_port *port, const u32 *pdo,
>>>>   }
>>>>   EXPORT_SYMBOL_GPL(tcpm_update_sink_capabilities);
>>>>
>>>> +/*
>>>> + * Don't call this function in interrupt context. Caller needs to free
>>> the
>>>> + * memory itself.
>>>> + */
>>>> +int tcpm_get_partner_src_caps(struct tcpm_port *port, u32 **src_pdo)
>>>> +{
>>>> +     unsigned int nr_pdo;
>>>> +
>>>> +     if (port->nr_source_caps == 0)
>>>> +             return -ENODATA;
>>>> +
>>>> +     *src_pdo = kcalloc(port->nr_source_caps, sizeof(u32), GFP_KERNEL);
>>>> +     if (!src_pdo)
>>>> +             return -ENOMEM;
>>>> +
>>>> +     mutex_lock(&port->lock);
>>>> +     nr_pdo = tcpm_copy_pdos(*src_pdo, port->source_caps,
>>>> +                             port->nr_source_caps);
>>>> +     mutex_unlock(&port->lock);
>>>> +     return nr_pdo;
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(tcpm_get_partner_src_caps);
>>>
>>> We don't add new functions that no one uses :(
>>>
>>>
>> This function is useful if the PD Device Policy Manager is implemented
>> outside of TCPM.
>> In this situation, Device Policy Manager needs to know the partner
>> capabilities to optimize
>> the charging process.
> 
> And where is that code?
> 

Agreed - that code should be sent upstream as well to let us see the
entire context.

>> Take existing functions in TCPM for example:
>> Function "tcpm_update_sink_capabilities" and
>> "tcpm_update_source_capabilities" are exposed
>> as well. And no one uses them now.
> 
> Great, let's go delete them now, we should not have apis that no one
> uses.  This isn't a new thing...
> 

I sent a patch to do just that. Quite frankly I don't recal
why I thought those functions might be needed.

Guenter