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

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Date:	Wed, 03 Mar 2010 13:40:49 +0300
From:	Sergei Shtylyov <sshtylyov@...sta.com>
To:	Jeff Garzik <jeff@...zik.org>
CC:	Sergei Shtylyov <sshtylyov@...sta.com>,
	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()

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. :-)

>     Jeff

MBR, Sergei

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