linux-kernel - Re: [PATCH 1/6 v10] ARM: Add basic architecture support for VIA/WonderMedia 85xx SoC's

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Message-ID: <AANLkTinZEhJ8aUe63yc_BNdifn_5g8U=iStwwXEU-+V9@mail.gmail.com>
Date:	Thu, 23 Dec 2010 01:02:11 +0300
From:	Alexey Charkov <alchark@...il.com>
To:	Ryan Mallon <ryan@...ewatersys.com>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	linux-arm-kernel@...ts.infradead.org,
	vt8500-wm8505-linux-kernel@...glegroups.com,
	Eric Miao <eric.y.miao@...il.com>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>,
	Albin Tonnerre <albin.tonnerre@...e-electrons.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6 v10] ARM: Add basic architecture support for
 VIA/WonderMedia 85xx SoC's

2010/12/23 Ryan Mallon <ryan@...ewatersys.com>:
> On 12/23/2010 10:18 AM, Alexey Charkov wrote:
>> This adds support for the family of Systems-on-Chip produced initially
>> by VIA and now its subsidiary WonderMedia that have recently become
>> widespread in lower-end Chinese ARM-based tablets and netbooks.
>>
>> Support is included for both VT8500 and WM8505, selectable by a
>> configuration switch at kernel build time.
>>
>> Included are basic machine initialization files, register and
>> interrupt definitions, support for the on-chip interrupt controller,
>> high-precision OS timer, GPIO lines, necessary macros for early debug,
>> pulse-width-modulated outputs control, as well as platform device
>> configurations for the specific drivers implemented elsewhere.
>>
>> Signed-off-by: Alexey Charkov <alchark@...il.com>
>> ---
>>
>> Welcome the jubilee tenth revision of this patch ;-)
>>
>> I've tried to incorporate the suggestions by Ryan and Arnd, hope that
>> there is nothing left out. There was a massive reorganization of code
>> to remove less-than-obvious magic with MMIO registers and irqs being
>> held in huge structs, now they are again macro definitions. Those
>> macros are, however, only included in single isolated files, and
>> actual values to use are chosen at runtime by calling the respective
>> routines at machine initialization. There are also stylistic changes
>> all around, where Ryan suggested.
>>
>> As a result, i8042 should again be adjusted a bit to reflect the new
>> place to find respective register/irq definitions, that one will be
>> sent in the respective thread shortly.
>>
>> Best regards,
>> Alexey
>
> <snip>
>
>> --- /dev/null
>> +++ b/arch/arm/mach-vt8500/devices-vt8500.c
>> @@ -0,0 +1,117 @@
>> +/* linux/arch/arm/mach-vt8500/devices-vt8500.c
>> + *
>> + * Copyright (C) 2010 Alexey Charkov <alchark@...il.com>
>> + *
>> + * This software is licensed under the terms of the GNU General Public
>> + * License version 2, as published by the Free Software Foundation, and
>> + * may be copied, distributed, and modified under those terms.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> + * GNU General Public License for more details.
>> + *
>> + */
>> +
>> +#include <linux/platform_device.h>
>> +
>> +#include <mach/vt8500_regs.h>
>> +#include <mach/vt8500_irqs.h>
>> +#include <mach/i8042.h>
>> +#include "devices.h"
>> +
>> +static inline struct resource WMT_MMIO_RES(u32 start, u32 size)
>> +{
>> +     struct resource tmp = {
>> +             .flags = IORESOURCE_MEM,
>> +             .start = start,
>> +             .end = start + size - 1,
>> +     };
>> +
>> +     return tmp;
>> +}
>
> These functions can be marked __init (though I guess they already are if
> marked inline?). They should also have lower case names since they are
> proper functions.
>

As inline functions are unrolled into the caller at compile time, and
the caller is __init, I would expect their code to be freed after init
as well. I could be wrong, though :)

> Do these functions generate warnings about returning temporary values
> off the stack? If so, they could be rewritten as:
>

Should those be compile-time or run-time? I did not see any.

> static __init void wmt_mmio_res(struct resource *res,
>                                u32 start, u32 size)
> {
>        res->flags = IORESOURCE_MEM;
>        res->start = start;
>        res->end   = start + size - 1;
> }
>
> You could also make these functions static inline in devices.h to avoid
> having to define them for each board.
>

Agreed.

>> +
>> +static inline struct resource WMT_IRQ_RES(int irq)
>> +{
>> +     struct resource tmp = {
>> +             .flags = IORESOURCE_IRQ,
>> +             .start = irq,
>> +             .end = irq,
>> +     };
>> +
>> +     return tmp;
>> +}
>> +
>> +#define WMT_RES_ADD(__device, __resource, __num) \
>> +if (platform_device_add_resources(__device, __resource, __num)) \
>> +     pr_err("Failed to assign resources to __device##\n");
>
> This could be written as a proper function. The resource add is unlikely
> to fail. Maybe keep the warning but don't worry about printing the
> device name?
>

There is memory allocation inside platform_device_add_resources, so
probably there is scope for failure. I could add unlikely(), though.

Thanks,
Alexey
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