linux-kernel - Re: [PATCH 4/6] fpga: region: change fpga_region

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Date:   Thu, 29 Mar 2018 15:42:51 -0500
From:   Alan Tull <atull@...nel.org>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Moritz Fischer <mdf@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-fpga@...r.kernel.org
Subject: Re: [PATCH 4/6] fpga: region: change fpga_region_register to have one param

On Thu, Mar 29, 2018 at 12:06 PM, Greg KH <gregkh@...uxfoundation.org> wrote:

Hi Greg,

>> -int fpga_region_register(struct device *dev, struct fpga_region *region)
>> +int fpga_region_register(struct fpga_region *region)
>>  {
>> +     struct device *dev = region->parent;
>>       int id, ret = 0;
>>
>> +     if (!dev) {
>> +             pr_err("Attempt to register fpga region without parent\n");
>> +             return -EINVAL;
>> +     }
>
> Are you sure you don't want a virtual device?  That is what will happen
> if you do not have a parent, right?  Or do you always want to have
> "real" devices?

I don't want to restrict this to "real" devices, so yes, I'll be
removing this check.

>> diff --git a/include/linux/fpga/fpga-region.h b/include/linux/fpga/fpga-region.h
>> index b6520318ab9c..423c87e3e29a 100644
>> --- a/include/linux/fpga/fpga-region.h
>> +++ b/include/linux/fpga/fpga-region.h
>> @@ -8,6 +8,7 @@
>>  /**
>>   * struct fpga_region - FPGA Region structure
>>   * @dev: FPGA Region device
>> + * @parent: parent device
>>   * @mutex: enforces exclusive reference to region
>>   * @bridge_list: list of FPGA bridges specified in region
>>   * @mgr: FPGA manager
>> @@ -18,6 +19,7 @@
>>   */
>>  struct fpga_region {
>>       struct device dev;
>> +     struct device *parent;
>
> Why doesn't your dev parent pointer point to this, why do you need to
> have a separate pointer?  That feels really wrong.  Pass in the parent
> pointer when you create the struct device, otherwise it will be
> registered incorrectly anyway.  Then you always have the correct
> pointer, no need to keep a "spare" copy.

I'll add a fpga_mgr_create function and let it set the parent.  No
need to save it.

Thanks again for the review,
Alan

>
> thanks,
>
> greg k-h