linux-kernel - Re: [PATCH v4 13/14] gunyah: rsc_mgr: Add auxiliary devices for console

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Date:   Fri, 30 Sep 2022 14:19:11 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Elliot Berman <quic_eberman@...cinc.com>
Cc:     Bjorn Andersson <quic_bjorande@...cinc.com>,
        Murali Nalajala <quic_mnalajal@...cinc.com>,
        Trilok Soni <quic_tsoni@...cinc.com>,
        Srivatsa Vaddagiri <quic_svaddagi@...cinc.com>,
        Carl van Schaik <quic_cvanscha@...cinc.com>,
        Andy Gross <agross@...nel.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Jassi Brar <jassisinghbrar@...il.com>,
        linux-arm-kernel@...ts.infradead.org,
        Mark Rutland <mark.rutland@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        Marc Zyngier <maz@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jonathan Corbet <corbet@....net>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Arnd Bergmann <arnd@...db.de>, devicetree@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 13/14] gunyah: rsc_mgr: Add auxiliary devices for
 console

On Wed, Sep 28, 2022 at 12:56:32PM -0700, Elliot Berman wrote:
> Gunyah resource manager exposes a concrete functionalities which
> complicate a single resource manager driver.

I am sorry, but I do not understand this sentance.  What is so
complicated about individual devices being created?  Where are they
created?  What bus?

Use auxiliary bus
> to help split high level functions for the resource manager and keep the
> primary resource manager driver focused on the RPC with RM itself.
> Delegate Resource Manager's console functionality to the auxiliary bus.
> 
> Signed-off-by: Elliot Berman <quic_eberman@...cinc.com>
> ---
>  drivers/virt/gunyah/Kconfig   |  1 +
>  drivers/virt/gunyah/rsc_mgr.c | 21 +++++++++++++++++++++
>  2 files changed, 22 insertions(+)
> 
> diff --git a/drivers/virt/gunyah/Kconfig b/drivers/virt/gunyah/Kconfig
> index 78deed3c4562..610c8586005b 100644
> --- a/drivers/virt/gunyah/Kconfig
> +++ b/drivers/virt/gunyah/Kconfig
> @@ -17,6 +17,7 @@ config GUNYAH_RESORUCE_MANAGER
>  	tristate "Gunyah Resource Manager"
>  	select MAILBOX
>  	select GUNYAH_MESSAGE_QUEUES
> +	select AUXILIARY_BUS
>  	default y
>  	help
>  	  The resource manager (RM) is a privileged application VM supporting
> diff --git a/drivers/virt/gunyah/rsc_mgr.c b/drivers/virt/gunyah/rsc_mgr.c
> index 7f7e89a6436b..435fe0149915 100644
> --- a/drivers/virt/gunyah/rsc_mgr.c
> +++ b/drivers/virt/gunyah/rsc_mgr.c
> @@ -16,6 +16,7 @@
>  #include <linux/notifier.h>
>  #include <linux/workqueue.h>
>  #include <linux/completion.h>
> +#include <linux/auxiliary_bus.h>
>  #include <linux/gunyah_rsc_mgr.h>
>  #include <linux/platform_device.h>
>  
> @@ -98,6 +99,8 @@ struct gh_rsc_mgr {
>  	struct mutex send_lock;
>  
>  	struct work_struct recv_work;
> +
> +	struct auxiliary_device console_adev;
>  };
>  
>  static struct gh_rsc_mgr *__rsc_mgr;
> @@ -573,13 +576,31 @@ static int gh_rm_drv_probe(struct platform_device *pdev)
>  
>  	__rsc_mgr = rsc_mgr;
>  
> +	rsc_mgr->console_adev.dev.parent = &pdev->dev;
> +	rsc_mgr->console_adev.name = "console";
> +	ret = auxiliary_device_init(&rsc_mgr->console_adev);
> +	if (ret)
> +		goto err_msgq;
> +	ret = auxiliary_device_add(&rsc_mgr->console_adev);
> +	if (ret)
> +		goto err_console_adev_uninit;
> +
>  	return 0;
> +
> +err_console_adev_uninit:
> +	auxiliary_device_uninit(&rsc_mgr->console_adev);
> +err_msgq:
> +	gunyah_msgq_remove(&rsc_mgr->msgq);
> +	return ret;
>  }

Why can't you just have individual platform devices for the individual
devices your hypervisor exposes?

You control the platform devices, why force them to be shared like this?

thanks,

greg k-h