linux-kernel - Re: [PATCH 2/2 v2] sata highbank: add bit-banged SGPIO driver support

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Date:	Wed, 05 Jun 2013 15:19:30 -0500
From:	Mark Langsdorf <mark.langsdorf@...xeda.com>
To:	Tejun Heo <tj@...nel.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-ide@...r.kernel.org" <linux-ide@...r.kernel.org>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Rob Herring <rob.herring@...xeda.com>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>
Subject: Re: [PATCH 2/2 v2] sata highbank: add bit-banged SGPIO driver support

On 06/04/2013 03:32 PM, Tejun Heo wrote:
> Hello, Mark.
> 
> On Tue, Jun 04, 2013 at 10:09:41AM -0500, Mark Langsdorf wrote:
>>> And tell ahci core sizeof(ecx_host_priv) some way, but really, just
>>> having a plain pointer should be enough, I think.
>>
>> I think I want to do the opposite. For 90% of the AHCI EM functions,
>> I want ecx_host_priv to be an ahci_host_priv so that I can use those
>> functions without having to keep a local copy of them.
>>
>> Would something like this:
>> struct ahci_host_priv {
>> 	/* standard AHCI existing stuff */
>> 	void *private_data;
>> };
>>
>> I shied away from that because a private data structure having a private
>> data structure doesn't seem right.
> 
> Aren't we talking about the same thing?  I'm perfectly fine with
> adding a pointer to ahci_host_priv.  Maybe you can name it slightly
> differently - say, *impl_data, *platform_data, whatever.

I guess we are talking about the same thing. I'll do that.

>>>> +static ssize_t ecx_transmit_led_message(struct ata_port *ap, u32 state,
>>>> +					ssize_t size)
>>>> +{
>>> ...
>>>> +	if (!hpriv->em_msg_type & EM_MSG_TYPE_LED)
>>>> +		return size;
>>>
>>> Is this really correct?  You first negate and convert it to bool and
>>> then bit-wise and it with a mask?  How is supposed to work?
>>
>> Am I confused about the order of operations? It's meant to be "continue
>> if hpriv->em_msg_type doesn't have EM_MSG_TYPE_LED set".
> 
> Shouldn't that be
> 
> 	if (!(hpriv->em_msg_type & EM_MSG_TYPE_LED))
> 
> ! has higher priority than &.  You're converting em_msg_type to 1 or 0
>   and then and'ing EM_MSG_TYPE_LED to it.

I'll fix it then.

--Mark Langsdorf
Calxeda, Inc.
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