linux-kernel - Re: [PATCH 09/12] ahci: Introduce ahci_set_em

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Date:	Wed, 03 Mar 2010 06:41:58 -0500
From:	Jeff Garzik <jeff@...zik.org>
To:	Sergei Shtylyov <sshtylyov@...sta.com>
CC:	Anton Vorontsov <avorontsov@...mvista.com>,
	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 09/12] ahci: Introduce ahci_set_em_messages()

On 03/03/2010 05:40 AM, Sergei Shtylyov wrote:
> Hello.
>
> Jeff Garzik wrote:
>
>>>> Factor out some ahci_em_messages handling code from ahci_init_one().
>>>> We would like to reuse it for non-PCI devices.
>>>>
>>>> Signed-off-by: Anton Vorontsov <avorontsov@...mvista.com>
>>>> ---
>>>> drivers/ata/ahci.c | 41 ++++++++++++++++++++++++-----------------
>>>> 1 files changed, 24 insertions(+), 17 deletions(-)
>>>>
>>>> diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
>>>> index 18443e9..6694b17 100644
>>>> --- a/drivers/ata/ahci.c
>>>> +++ b/drivers/ata/ahci.c
>>>> @@ -3040,6 +3040,29 @@ static inline void
>>>> ahci_gtf_filter_workaround(struct ata_host *host)
>>>> {}
>>>> #endif
>>>>
>>>> +static void ahci_set_em_messages(struct ahci_host_priv *hpriv,
>>>> + struct ata_port_info *pi)
>>>> +{
>>>> + u8 messages;
>>>> + void __iomem *mmio = hpriv->mmio;
>>>> + u32 em_loc = readl(mmio + HOST_EM_LOC);
>>>> + u32 em_ctl = readl(mmio + HOST_EM_CTL);
>>>> +
>>>> + if (!ahci_em_messages || !(hpriv->cap & HOST_CAP_EMS))
>>>> + return;
>>>> +
>>>> + messages = (em_ctl & EM_CTRL_MSG_TYPE) >> 16;
>>>> +
>>>> + /* we only support LED message type right now */
>>>> + if ((messages & 0x01) && (ahci_em_messages == 1)) {
>>>> + /* store em_loc */
>>>> + hpriv->em_loc = ((em_loc >> 16) * 4);
>>>
>>> Could drop unneeded parens, while at it...
>>
>> While not strictly necessary, parens often help with readability. I
>> think the above code looks fine as-is. If the reader has to waste a
>> few seconds recalling C's operator precedence, that detracts from the
>> easy reading of the code. Not everyone is like me and has worked on a
>> C compiler, you know ;-)
>
> Come on, parens around the right arg of = are pretty counter-intuitive
> and so don't add to the readability. :-)

<shrug>  I respectfully disagree.  It is wasteful but does not detract 
from readability at all, IMO.

	Jeff



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