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SubjectRe: [PATCH v10 08/26] gunyah: rsc_mgr: Add resource manager RPC core
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On 2/16/2023 11:37 PM, Greg Kroah-Hartman wrote:
> On Thu, Feb 16, 2023 at 09:40:52AM -0800, Elliot Berman wrote:
>>
>>
>> On 2/15/2023 10:43 PM, Greg Kroah-Hartman wrote:
>>> On Tue, Feb 14, 2023 at 01:23:25PM -0800, Elliot Berman wrote:
>>>> +struct gh_rm {
>>>> + struct device *dev;
>>>
>>> What device does this point to?
>>>
>>
>> The platform device.
>
> What platform device? And why a platform device?
>

This will be used for the dev_printk. It's presently also used for the
reference counting. From your comments below, I'll switch the reference
counting away from this platform device.

>>>> + struct gunyah_resource tx_ghrsc, rx_ghrsc;
>>>> + struct gh_msgq msgq;
>>>> + struct mbox_client msgq_client;
>>>> + struct gh_rm_connection *active_rx_connection;
>>>> + int last_tx_ret;
>>>> +
>>>> + struct idr call_idr;
>>>> + struct mutex call_idr_lock;
>>>> +
>>>> + struct kmem_cache *cache;
>>>> + struct mutex send_lock;
>>>> + struct blocking_notifier_head nh;
>>>> +};
>>>
>>> This obviously is the "device" that your system works on, so what are
>>> the lifetime rules of it? Why isn't is just a real 'struct device' in
>>> the system instead of a random memory blob with a pointer to a device?
>>>
>>> What controls the lifetime of this structure and where is the reference
>>> counting logic for it?
>>>
>>
>> The lifetime of the structure is bound by the platform device that above
>> struct device *dev points to. get_gh_rm and put_gh_rm increments the device
>> ref counter and ensures lifetime of the struct is also extended.
>
> But this really is "your" device, not the platform device. So make it a
> real one please as that is how the kernel's driver model works. Don't
> hang "magic structures" off of a random struct device and have them
> control the lifetime rules of the parent without actually being a device
> themself. This should make things simpler overall, not more complex,
> and allow you to expose things to userspace properly (right now your
> data is totally hidden.)

The "real" device I create here is the miscdev, so I think the
recommendation here is to do refcounting off that miscdev. Is this the
approach you were thinking of?

Thanks,
Elliot

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