linux-kernel - Re: [RFC V1 2/7] drivers/base: Introduce callbacks for IMS interrupt domain

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Date:   Fri, 13 Sep 2019 05:39:10 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Megha Dey <megha.dey@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-pci@...r.kernel.org, maz@...nel.org, bhelgaas@...gle.com,
        rafael@...nel.org, tglx@...utronix.de, hpa@...or.com,
        alex.williamson@...hat.com, jgg@...lanox.com, ashok.raj@...el.com,
        megha.dey@...el.com, jacob.jun.pan@...el.com,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Sanjay Kumar <sanjay.k.kumar@...el.com>
Subject: Re: [RFC V1 2/7] drivers/base: Introduce callbacks for IMS interrupt
 domain

On Thu, Sep 12, 2019 at 06:32:03PM -0700, Megha Dey wrote:
> This patch serves as a preparatory patch to introduce a new IMS
> (Interrupt Message Store) domain. It consists of APIs which would
> be used as callbacks to the IRQ chip associated with the IMS domain.
> 
> The APIs introduced in this patch are:
> dev_ims_mask_irq - Generic irq chip callback to mask IMS interrupts
> dev_ims_unmask_irq - Generic irq chip callback to unmask IMS interrupts
> dev_ims_domain_write_msg - Helper to write MSI message to Device IMS
> 
> It also introduces IMS specific structures namely:
> dev_ims_ops - Callbacks for IMS domain ops
> dev_ims_desc - Device specific IMS msi descriptor data
> dev_ims_priv_data - Internal data structure containing a unique devid
> and a pointer to the IMS domain ops
> 
> Lastly, it adds a new config option MSI_IMS which must be enabled by
> any driver who would want to use the IMS infrastructure.
> 
> Since IMS is not PCI compliant (like platform-msi), most of the code is
> similar to platform-msi.c.
> 
> TODO: Conclude if ims-msi.c and platform-msi.c can be merged.
> 
> Cc: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> Signed-off-by: Sanjay Kumar <sanjay.k.kumar@...el.com>
> Signed-off-by: Megha Dey <megha.dey@...ux.intel.com>
> ---
>  drivers/base/Kconfig   |  7 ++++
>  drivers/base/Makefile  |  1 +
>  drivers/base/ims-msi.c | 94 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/msi.h    | 35 ++++++++++++++++++-
>  4 files changed, 136 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/base/ims-msi.c
> 
> diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
> index dc40449..038fabd 100644
> --- a/drivers/base/Kconfig
> +++ b/drivers/base/Kconfig
> @@ -206,3 +206,10 @@ config GENERIC_ARCH_TOPOLOGY
>  	  runtime.
>  
>  endmenu
> +
> +config MSI_IMS
> +	bool "Device Specific Interrupt Message Storage (IMS)"
> +	select GENERIC_MSI_IRQ
> +	help
> +	  This allows device drivers to enable device specific
> +	  interrupt message storage (IMS) besides standard MSI-X interrupts.

This text tells me nothing about if I want to enable this or not.  How
is a user (or even a developer) supposed to know if their hardware
requires this?

And I _really_ dont want to see this in drivers/base/ if at all possible
because suddenly I am responsible for this code that I know nothing
about.

greg k-h