linux-kernel - Re: [PATCH] genirq/msi: Add the address and data that show MSI/MSIX

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Message-ID: <877c5be0no.ffs@tglx>
Date: Thu, 27 Feb 2025 18:51:39 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, Hans Zhang
 <18255117159@....com>
Cc: kw@...ux.com, kwilczynski@...nel.org, bhelgaas@...gle.com,
 cassel@...nel.org, linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] genirq/msi: Add the address and data that show MSI/MSIX

On Thu, Feb 27 2025 at 22:09, Manivannan Sadhasivam wrote:
> On Fri, Feb 28, 2025 at 12:28:21AM +0800, Hans Zhang wrote:
>> +	return sysfs_emit(
>> +		buf,
>> +		"%s\n address_hi: 0x%08x\n address_lo: 0x%08x\n msg_data: 0x%08x\n",
>> +		is_msix ? "msix" : "msi", desc->msg.address_hi,
>> +		desc->msg.address_lo, desc->msg.data);
>
> Sysfs is an ABI. You cannot change the semantics of an attribute.

Correct. Aside of that this is debug information and has no business in
sysfs.

The obvious place to expose this is via the existing debugfs irq/*
mechanism. All it requires is to implement a debug_show() callback in
the MSI core code and assign it to domain ops::debug_show() on domain
creation, if it does not provide its own callback.

Thanks,

        tglx