Re: [PATCH v5 1/3] misc: fastrpc: iterate CB nodes manually instead of of_platform_populate

[Ekansh Gupta <ekansh.gupta@oss.qualcomm.com>]

On 23-09-2026 14:09, Vinayak Katoch wrote:
> of_platform_populate() only guarantees that child devices are registered,
> not that their probes have completed before it returns. This creates a
> window where fastrpc_cb_init() may not have run for all context bank
> nodes, leaving the channel context partially initialised.
> 
> Introduce fastrpc_cb_devices_create() to iterate over child DT nodes
> directly and call fastrpc_cb_init() synchronously for each
> qcom,fastrpc-compute-cb node. This ensures all context banks are fully
> initialised before fastrpc_rpmsg_probe() returns.
> 
> Introduce fastrpc_cb_devices_destroy() as the symmetric counterpart.
> Before destroying the CB platform devices, invalidate all sessions under
> the channel lock so that any fastrpc_user still holding a reference to
> the channel context cannot acquire a new session backed by a destroyed
> device.
> 
> Since fastrpc_cb_driver is no longer needed as an independent platform
> driver, remove it along with its match table and remove callback. Use
> module_rpmsg_driver() now that only a single driver registration remains.
> 
> Signed-off-by: Vinayak Katoch <vinayak.katoch@oss.qualcomm.com>
> ---
>  drivers/misc/fastrpc.c | 104 ++++++++++++++++++++++++-------------------------
>  1 file changed, 52 insertions(+), 52 deletions(-)
> 
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index af18ff1992ee..f20d3e5ecc81 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -2333,7 +2333,7 @@ static const struct file_operations fastrpc_fops = {
>  	.compat_ioctl = fastrpc_device_ioctl,
>  };
>  
> -static int fastrpc_cb_probe(struct platform_device *pdev)
> +static int fastrpc_cb_init(struct platform_device *pdev)
>  {
>  	struct fastrpc_channel_ctx *cctx;
>  	struct fastrpc_session_ctx *sess;
> @@ -2355,7 +2355,7 @@ static int fastrpc_cb_probe(struct platform_device *pdev)
>  	spin_lock_irqsave(&cctx->lock, flags);
>  	if (cctx->sesscount >= FASTRPC_MAX_SESSIONS) {
>  		spin_unlock_irqrestore(&cctx->lock, flags);
> -		dev_err(&pdev->dev, "too many sessions\n");
> +		dev_err(dev, "too many sessions\n");
>  		return -ENOSPC;
>  	}
>  	dma_bits = cctx->soc_data->dma_addr_bits_default;
> @@ -2389,37 +2389,63 @@ static int fastrpc_cb_probe(struct platform_device *pdev)
>  	return 0;
>  }
>  
> -static void fastrpc_cb_remove(struct platform_device *pdev)
> +static void fastrpc_cb_devices_destroy(struct rpmsg_device *rpdev)
>  {
> -	struct fastrpc_channel_ctx *cctx = dev_get_drvdata(pdev->dev.parent);
> -	struct fastrpc_session_ctx *sess = dev_get_drvdata(&pdev->dev);
if this dev_get_drvdata() is not used, can you also remove
dev_set_drvdata()?> +	struct fastrpc_channel_ctx *cctx =
dev_get_drvdata(&rpdev->dev);
> +	struct device *rdev = &rpdev->dev;
> +	struct platform_device *pdev;
> +	struct device_node *np;
>  	unsigned long flags;
>  	int i;
>  
>  	spin_lock_irqsave(&cctx->lock, flags);
> -	for (i = 0; i < FASTRPC_MAX_SESSIONS; i++) {
> -		if (cctx->session[i].sid == sess->sid) {
> -			cctx->session[i].valid = false;
> -			cctx->sesscount--;
> +	for (i = 0; i < cctx->sesscount; i++)
> +		cctx->session[i].valid = false;
> +	spin_unlock_irqrestore(&cctx->lock, flags);
> +
> +	for_each_available_child_of_node(rdev->of_node, np) {
> +		if (!of_device_is_compatible(np, "qcom,fastrpc-compute-cb")) {
can there be any such case?> +			of_node_put(np);
> +			continue;
>  		}
> +
> +		pdev = of_find_device_by_node(np);
> +		of_node_put(np);
> +		if (pdev)
> +			of_platform_device_destroy(&pdev->dev, NULL);
>  	}
can you check if this works here instead of above blob:
device_for_each_child_reverse(rdev, NULL, of_platform_device_destroy);>
-	spin_unlock_irqrestore(&cctx->lock, flags);
>  }
>  
> -static const struct of_device_id fastrpc_match_table[] = {
> -	{ .compatible = "qcom,fastrpc-compute-cb" },
> -	{ }
> -};
> +static int fastrpc_cb_devices_create(struct rpmsg_device *rpdev)
> +{
> +	struct device *rdev = &rpdev->dev;
> +	struct platform_device *pdev;
> +	struct device_node *np;
> +	int err;
>  
> -static struct platform_driver fastrpc_cb_driver = {
> -	.probe = fastrpc_cb_probe,
> -	.remove = fastrpc_cb_remove,
> -	.driver = {
> -		.name = "qcom,fastrpc-cb",
> -		.of_match_table = fastrpc_match_table,
> -		.suppress_bind_attrs = true,
> -	},
> -};
> +	for_each_available_child_of_node(rdev->of_node, np) {
> +		if (!of_device_is_compatible(np, "qcom,fastrpc-compute-cb")) {
> +			of_node_put(np);
> +			continue;
> +		}
> +
> +		pdev = of_platform_device_create(np, NULL, rdev);
> +		if (!pdev) {
> +			of_node_put(np);
> +			fastrpc_cb_devices_destroy(rpdev);
> +			return -EINVAL;
-ENODEV?> +		}
> +
> +		err = fastrpc_cb_init(pdev);
> +		if (err) {
> +			of_node_put(np);
> +			fastrpc_cb_devices_destroy(rpdev);
> +			return err;
> +		}
> +	}
> +
> +	return 0;
> +}
>  
>  static int fastrpc_device_register(struct device *dev, struct fastrpc_channel_ctx *cctx,
>  				   bool is_secured, const char *domain)
> @@ -2639,7 +2665,7 @@ static int fastrpc_rpmsg_probe(struct rpmsg_device *rpdev)
>  	data->rpdev = rpdev;
>  	dev_set_drvdata(&rpdev->dev, data);
>  
> -	err = of_platform_populate(rdev->of_node, NULL, NULL, rdev);
> +	err = fastrpc_cb_devices_create(rpdev);
>  	if (err)
>  		goto err_deregister_fdev;
>  
> @@ -2711,7 +2737,7 @@ static void fastrpc_rpmsg_remove(struct rpmsg_device *rpdev)
>  				&cctx->remote_heap_addr, cctx->remote_heap_size, err);
>  	}
>  
> -	of_platform_depopulate(&rpdev->dev);
> +	fastrpc_cb_devices_destroy(rpdev);
>  
>  	fastrpc_channel_ctx_put(cctx);
>  }
> @@ -2798,33 +2824,7 @@ static struct rpmsg_driver fastrpc_driver = {
>  	},
>  };
>  
> -static int fastrpc_init(void)
> -{
> -	int ret;
> -
> -	ret = platform_driver_register(&fastrpc_cb_driver);
> -	if (ret < 0) {
> -		pr_err("fastrpc: failed to register cb driver\n");
> -		return ret;
> -	}
> -
> -	ret = register_rpmsg_driver(&fastrpc_driver);
> -	if (ret < 0) {
> -		pr_err("fastrpc: failed to register rpmsg driver\n");
> -		platform_driver_unregister(&fastrpc_cb_driver);
> -		return ret;
> -	}
> -
> -	return 0;
> -}
> -module_init(fastrpc_init);
> -
> -static void fastrpc_exit(void)
> -{
> -	platform_driver_unregister(&fastrpc_cb_driver);
> -	unregister_rpmsg_driver(&fastrpc_driver);
> -}
> -module_exit(fastrpc_exit);
> +module_rpmsg_driver(fastrpc_driver);
>  
>  MODULE_DESCRIPTION("Qualcomm FastRPC");
>  MODULE_LICENSE("GPL v2");
>