linux-kernel - Re: [PATCH] PCI: qcom: Add support for modular builds

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Date:   Thu, 14 Jul 2022 15:10:29 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Stanimir Varbanov <svarbanov@...sol.com>
Cc:     Johan Hovold <johan+linaro@...nel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        linux-pci@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: qcom: Add support for modular builds

On Thu, Jul 14, 2022 at 03:19:49PM +0300, Stanimir Varbanov wrote:
> Hi Johan,
> 
> Please take a look why we made it built-in first [1].
> 
> If arguments there are still valid I don't see why to make it a module
> again.

Yeah, I've seen that patch, and many just like that one by the same
author, and I don't think the arguments spelled out there are valid.

Sure, the Kconfig symbol for this driver was bool at the time so the
remove() code could not have received much testing, but the patch
ignores the fact that preventing drivers to be built as modules is
detrimental to multi-platform builds (e.g. Android GKI).

As I mention in passing below, being able to build a driver as a module
is also really useful during development. Not least to be able to test
power-sequencing and making sure that you're not unknowingly relying on
boot firmware to have set things up for you.

> [1] https://lkml.org/lkml/2016/8/24/694
> 
> On 5/19/22 12:46, Johan Hovold wrote:
> > Allow the Qualcomm PCIe controller driver to be built as a module, which
> > is useful for multi-platform kernels as well as during development.
> > 
> > Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> > ---
> >  drivers/pci/controller/dwc/Kconfig     |  2 +-
> >  drivers/pci/controller/dwc/pcie-qcom.c | 36 +++++++++++++++++++++++---
> >  2 files changed, 34 insertions(+), 4 deletions(-)

Johan