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Subject: Re: [PATCH 1/4] amba: Export amba_bustype
To: Russell King - ARM Linux <linux@armlinux.org.uk>,
 Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Kim Phillips <kim.phillips@arm.com>,
 Mathieu Poirier <mathieu.poirier@linaro.org>,
 Alexander Shishkin <alexander.shishkin@linux.intel.com>,
 Alex Williamson <alex.williamson@redhat.com>,
 Andrew Morton <akpm@linux-foundation.org>,
 David Howells <dhowells@redhat.com>, Eric Auger <eric.auger@redhat.com>,
 Eric Biederman <ebiederm@xmission.com>, Gargi Sharma <gs051095@gmail.com>,
 Geert Uytterhoeven <geert+renesas@glider.be>,
 Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
 Kefeng Wang <wangkefeng.wang@huawei.com>, Kirill Tkhai
 <ktkhai@virtuozzo.com>, Mike Rapoport <rppt@linux.vnet.ibm.com>,
 Oleg Nesterov <oleg@redhat.com>, Pavel Tatashin <pasha.tatashin@oracle.com>,
 Rik van Riel <riel@redhat.com>, Thierry Reding <treding@nvidia.com>,
 Todd Kjos <tkjos@google.com>,
 linux-arm Mailing List <linux-arm-kernel@lists.infradead.org>,
 Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
References: <20180508140628.f30774c70c4c481bff3f8000@arm.com>
 <CAHp75VfGpS_QkLj4XM8uHW0BAJV0EBWZ_yLP0R2D+ok4Mt=SQg@mail.gmail.com>
 <20180516091841.GH16141@n2100.armlinux.org.uk>
From: Robin Murphy <robin.murphy@arm.com>
Message-ID: <f8ad28c9-df7b-5211-dbdf-bce4f24ece94@arm.com>
Date: Wed, 16 May 2018 12:12:23 +0100
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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@arm.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.