linux-kernel - Re: [RFC][PATCH V3] axi: add AXI bus driver

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Date:	Tue, 12 Apr 2011 13:40:36 +0200
From:	Rafał Miłecki <zajec5@...il.com>
To:	Greg KH <greg@...ah.com>
Cc:	linux-wireless@...r.kernel.org,
	"John W. Linville" <linville@...driver.com>,
	George Kashperko <george@...u.edu.ua>,
	Arnd Bergmann <arnd@...db.de>,
	Russell King <rmk@....linux.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	b43-dev@...ts.infradead.org,
	Michael Büsch <mb@...sch.de>,
	linuxdriverproject <devel@...uxdriverproject.org>,
	Andy Botting <andy@...ybotting.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Larry Finger <Larry.Finger@...inger.net>
Subject: Re: [RFC][PATCH V3] axi: add AXI bus driver

2011/4/12 Rafał Miłecki <zajec5@...il.com>:
> 2011/4/12 Greg KH <greg@...ah.com>:
>> On Tue, Apr 12, 2011 at 12:45:33AM +0200, Rafał Miłecki wrote:
>>> 2011/4/12 Greg KH <greg@...ah.com>:
>>> > Then in your release function, free the struct axi_device.  It's that
>>> > simple.  To try to free it before then would be wrong and cause
>>> > problems.
>>>
>>> This is because it is defined as:
>>> struct axi_device cores[AXI_MAX_NR_CORES];
>>
>> No way, seriously?
>>
>> You can't do that, no static struct devices please.  Make these dynamic
>> and everything will be fine.  The -mm tree used to have a huge warning
>> if you ever tried to register a statically allocated struct, but that
>> didn't really work out, but would have saved you a lot of time here,
>> sorry.
>>
>> So dynamically allocate the structures and you will be fine.
>
> Well, I saw that along kernel, I had no idea there is anything wrong
> about this. It seems more ppl do not know about this:
> struct radeon_ib        ibs[RADEON_IB_POOL_SIZE];
> struct radeon_pm_clock_info clock_info[8];
> struct radeon_pm_profile profiles[PM_PROFILE_MAX];
> struct radeon_surface_reg surface_regs[RADEON_GEM_MAX_SURFACES];
> struct radeon_i2c_chan *i2c_bus[RADEON_MAX_I2C_BUS];
>
> struct b43_key key[B43_NR_GROUP_KEYS * 2 + B43_NR_PAIRWISE_KEYS];
>
> struct ssb_device devices[SSB_MAX_NR_CORES];
> I guess I could fine more examples by simple grepping .h files.
>
> Is there some guide around with things like this we should avoid?
> checkpatch does no catch this, so maybe just some manual? Could you
> point me to it?

Greg, my:
struct ssb_device devices[SSB_MAX_NR_CORES];
is part of "struct axi_bus", which we allocate dynamically anyway:

struct axi_bus *bus;
bus = kzalloc(sizeof(*bus), GFP_KERNEL);
if (!bus)
	goto out;

So do we really need to dynamically alloc main structure and
separately every of it's array of structs? Does it really make sense?
Please point me to some place where I can read more about this. Some
tips about coding style for such things, cases.

-- 
Rafał
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