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In-Reply-To: <20051221190558.GD2361@parisc-linux.org>
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Subject: Re: [PATCH 2/4] msi vector targeting abstractions
Date: Wed, 21 Dec 2005 14:17:32 -0500
Message-ID: <Pine.LNX.4.61.0512211410200.12572@chaos.analogic.com>
Thread-Topic: [PATCH 2/4] msi vector targeting abstractions
Thread-Index: AcYGYzItaAO8sO0hTwOUVPbv6BtP1A==
References: <20051221184337.5003.85653.32527@attica.americas.sgi.com> <20051221184348.5003.7540.53186@attica.americas.sgi.com> <20051221190558.GD2361@parisc-linux.org>
From: "linux-os \(Dick Johnson\)" <linux-os@analogic.com>
To: "Matthew Wilcox" <matthew@wil.cx>
Cc: "Mark Maule" <maule@sgi.com>, <linux-ia64@vger.kernel.org>,
       <linux-kernel@vger.kernel.org>, "Tony Luck" <tony.luck@intel.com>
Reply-To: "linux-os \(Dick Johnson\)" <linux-os@analogic.com>
Sender: linux-kernel-owner@vger.kernel.org
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On Wed, 21 Dec 2005, Matthew Wilcox wrote:

> On Wed, Dec 21, 2005 at 12:42:41PM -0600, Mark Maule wrote:
>>  {
>>  	struct msi_desc *entry;
>> -	struct msg_address address;
>> +	uint32_t address_hi, address_lo;
>
> Don't use uint32_t.  Use u32 instead.
a>

But uint32_t is a correct POSIX type. Why would you smear its
use in the kernel when, in fact, one is not allowed to mix/match
kernel and user headers so it's impossible to pollute namespace?

>> @@ -108,28 +125,38 @@
>>     		if (!(pos = pci_find_capability(entry->dev, PCI_CAP_ID_MSI)))
>>  			return;
>>
>> +		pci_read_config_dword(entry->dev, msi_upper_address_reg(pos),
>> +			&address_hi);
>>  		pci_read_config_dword(entry->dev, msi_lower_address_reg(pos),
>> -			&address.lo_address.value);
>> -		address.lo_address.value &= MSI_ADDRESS_DEST_ID_MASK;
>> -		address.lo_address.value |= (cpu_physical_id(dest_cpu) <<
>> -									MSI_TARGET_CPU_SHIFT);
>> -		entry->msi_attrib.current_cpu = cpu_physical_id(dest_cpu);
>> +			&address_lo);
>> +
>> +		msi_callouts.msi_target(vector, dest_cpu,
>> +					&address_hi, &address_lo);
>> +
>> +		pci_write_config_dword(entry->dev, msi_upper_address_reg(pos),
>> +			address_hi);
>>  		pci_write_config_dword(entry->dev, msi_lower_address_reg(pos),
>> -			address.lo_address.value);
>> +			address_lo);
>
> But actually, I don't understand why you don't just pass a msg_address
> pointer to msi_target instead.
>
> (last two points apply throughtout this patch)
>
>>
>> +	(*msi_callouts.msi_teardown)(vector);
>> +
>
> Yuck.  There's a reason C allows you to call through function pointers as if
> they were functions.

The reason is to allow sloppy coding. The patch writer was properly
instructed to dereference function pointers. If you don't like
this "obviously correct" syntax there is no reason to force your
will on others.


Cheers,
Dick Johnson
Penguin : Linux version 2.6.13.4 on an i686 machine (5589.55 BogoMips).
Warning : 98.36% of all statistics are fiction.
.

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