linux-kernel - Re: [PATCH 1/4] amba: Export amba

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Date:   Wed, 16 May 2018 12:12:23 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Russell King - ARM Linux <linux@...linux.org.uk>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Kim Phillips <kim.phillips@....com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Howells <dhowells@...hat.com>,
        Eric Auger <eric.auger@...hat.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        Gargi Sharma <gs051095@...il.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Kirill Tkhai <ktkhai@...tuozzo.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Pavel Tatashin <pasha.tatashin@...cle.com>,
        Rik van Riel <riel@...hat.com>,
        Thierry Reding <treding@...dia.com>,
        Todd Kjos <tkjos@...gle.com>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] amba: Export amba_bustype

On 16/05/18 10:18, Russell King - ARM Linux wrote:
> On Wed, May 16, 2018 at 12:16:28PM +0300, Andy Shevchenko wrote:
>> On Tue, May 8, 2018 at 10:06 PM, Kim Phillips <kim.phillips@....com> wrote:
>>> This patch is provided in the context of allowing the Coresight driver
>>> subsystem to be loaded as modules.  Coresight uses amba_bus in its call
>>> to bus_find_device() in of_coresight_get_endpoint_device() when
>>> searching for a configurable endpoint device.  This patch allows
>>> Coresight to reference amba_bustype when built as a module.
>>
>>> --- a/drivers/amba/bus.c
>>> +++ b/drivers/amba/bus.c
>>> @@ -197,6 +197,7 @@ struct bus_type amba_bustype = {
>>>          .pm             = &amba_pm,
>>>          .force_dma      = true,
>>>   };
>>> +EXPORT_SYMBOL_GPL(amba_bustype);
>>
>> Oh,
>>
>> What wrong with the approach let's say similar to PCI bus?
>>
>> Whenever you have a struct device you may use two helpers:
>>
>> dev_is_pci() -> is the device of PCI bus type?
>> to_pci_dev() -> get's container of struct device for PCI bus case
> 
> How does that help with bus_find_device() which requires the bus_type
> structure for the type of devices to be searched?
Not to mention that dev_is_pci() still relies on pci_bus_type itself 
being exported anyway.

Robin.