linux-kernel - Re: [PATCH 1/1] staging: vchiq: Replace global state with per device state

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Message-ID: <84300618-98c8-0f44-e5a5-8d7fd6c853b0@i2se.com>
Date:   Mon, 1 Nov 2021 13:19:17 +0100
From:   Stefan Wahren <stefan.wahren@...e.com>
To:     Ojaswin Mujoo <ojaswin98@...il.com>, nsaenz@...nel.org,
        gregkh@...uxfoundation.org
Cc:     dan.carpenter@...cle.com, phil@...pberrypi.com,
        linux-arm-kernel@...ts.infradead.org,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] staging: vchiq: Replace global state with per device
 state

Hi Ojaswin,

Am 01.11.21 um 12:09 schrieb Ojaswin Mujoo:
> Currently, the driver has a global g_state variable which is initialised
> during probe and directly used all over the driver code. However, this
> prevents the driver to support multiple VideoCore VPUs at the same time.
>
> Replace this global state with a per device state which is initialised
> and allocated during probing.
>
> Signed-off-by: Ojaswin Mujoo <ojaswin98@...il.com>
...
>  
>  /*
> @@ -1763,6 +1795,7 @@ static int vchiq_probe(struct platform_device *pdev)
>  	struct device_node *fw_node;
>  	const struct of_device_id *of_id;
>  	struct vchiq_drvdata *drvdata;
> +	struct vchiq_device *vchiq_dev;
>  	int err;
>  
>  	of_id = of_match_node(vchiq_of_match, pdev->dev.of_node);
> @@ -1784,7 +1817,18 @@ static int vchiq_probe(struct platform_device *pdev)
>  
>  	platform_set_drvdata(pdev, drvdata);
>  
> -	err = vchiq_platform_init(pdev, &g_state);
> +	vchiq_dev = kzalloc(sizeof(struct vchiq_device), GFP_KERNEL);
> +	vchiq_dev->state = kzalloc(sizeof(struct vchiq_state), GFP_KERNEL);
> +	vchiq_dev->vchiq_pdev = *pdev;
> +
> +	g_state = vchiq_dev->state;
> +

just a quick idea: how about storing the global state within vchiq_drvdata?

So there is no need to reinvent somekind of vchiq device which is the
"same" as the platform device. After that you are able to access the
private driver data via platform_get_drvdata().

Best regards