linux-kernel - Re: [PATCH] PCI: endpoint: pci-epf-test: Move DMA check into read/write/copy functions

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Message-ID: <20240809184100.GA205407@bhelgaas>
Date: Fri, 9 Aug 2024 13:41:00 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Rick Wertenbroek <rick.wertenbroek@...il.com>
Cc: rick.wertenbroek@...g-vd.ch, dlemoal@...nel.org,
	alberto.dassatti@...g-vd.ch,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Niklas Cassel <cassel@...nel.org>, Frank Li <Frank.Li@....com>,
	Lars-Peter Clausen <lars@...afoo.de>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: endpoint: pci-epf-test: Move DMA check into
 read/write/copy functions

On Fri, Aug 09, 2024 at 08:56:29AM +0200, Rick Wertenbroek wrote:
> On Tue, Aug 6, 2024 at 9:15 PM Bjorn Helgaas <helgaas@...nel.org> wrote:
> > On Tue, Aug 06, 2024 at 06:27:54PM +0200, Rick Wertenbroek wrote:
> > > The test for a DMA transfer was done in pci_epf_test_cmd_handler, which
> > > if not supported would lead to the endpoint function just printing an
> > > error message and waiting for further commands. This would leave the
> >
> > I guess it's the *test* that prints the error message?  Is this the
> > "Cannot transfer data using DMA" message?
> 
> That is the error message, the error message is printed by the
> endpoint function, on the endpoint device. On the host side, nothing
> happens; the test program just hangs because the driver waits
> indefinitely. With the change I proposed, the test program completes
> the test and will display "NOT OKAY" as normal when a test fails.

Thanks for this; something like this would be helpful in the commit
log because it makes the two kernels involved more explicit.

Bjorn