linux-kernel - [PATCH V1 2/3] usb: misc: Add notifier call chain to Embedded USB Debug(EUD) driver

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Message-ID: <18212c7abbb8c833cc07f8500d4905b79c49ec59.1689148711.git.quic_schowdhu@quicinc.com>
Date:   Wed, 12 Jul 2023 13:52:39 +0530
From:   Souradeep Chowdhury <quic_schowdhu@...cinc.com>
To:     <linux-arm-msm@...r.kernel.org>, <linux-usb@...r.kernel.org>,
        Andy Gross <agross@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        "Bjorn Andersson" <andersson@...nel.org>,
        <gregkh@...uxfoundation.org>
CC:     <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        Sibi Sankar <quic_sibis@...cinc.com>,
        Rajendra Nayak <quic_rjendra@...cinc.com>,
        Souradeep Chowdhury <quic_schowdhu@...cinc.com>
Subject: [PATCH V1 2/3] usb: misc: Add notifier call chain to Embedded USB Debug(EUD) driver

Add the notifier call chain to EUD driver. The notifier call chain
is added to check the role-switch status of EUD. When multiple
modules are switching roles on the same port, they need to call this
notifier to check the role-switch status of EUD. If EUD is disabled,
then the modules can go for the role-switch, otherwise it needs to
be blocked. The notifier chain can be used to link multiple modules
switching roles on the same port and create a ordering, priority and
conflict resolution among them. The wrapper functions are defined here
which can be used to register a notifier block to the chain, deregister
it and also call the chain.

Signed-off-by: Souradeep Chowdhury <quic_schowdhu@...cinc.com>
---
 drivers/usb/misc/qcom_eud.c | 52 +++++++++++++++++++++++++++++++++++--
 1 file changed, 50 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/misc/qcom_eud.c b/drivers/usb/misc/qcom_eud.c
index 7f371ea1248c..e6c97a2cf2df 100644
--- a/drivers/usb/misc/qcom_eud.c
+++ b/drivers/usb/misc/qcom_eud.c
@@ -11,10 +11,13 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_platform.h>
 #include <linux/platform_device.h>
 #include <linux/slab.h>
 #include <linux/sysfs.h>
 #include <linux/usb/role.h>
+#include "qcom_eud_notifier.h"
 
 #define EUD_REG_INT1_EN_MASK	0x0024
 #define EUD_REG_INT_STATUS_1	0x0044
@@ -22,14 +25,16 @@
 #define EUD_REG_VBUS_INT_CLR	0x0080
 #define EUD_REG_CSR_EUD_EN	0x1014
 #define EUD_REG_SW_ATTACH_DET	0x1018
-#define EUD_REG_EUD_EN2		0x0000
+#define EUD_REG_EUD_EN2        0x0000
 
 #define EUD_ENABLE		BIT(0)
-#define EUD_INT_PET_EUD		BIT(0)
+#define EUD_INT_PET_EUD	BIT(0)
 #define EUD_INT_VBUS		BIT(2)
 #define EUD_INT_SAFE_MODE	BIT(4)
 #define EUD_INT_ALL		(EUD_INT_VBUS | EUD_INT_SAFE_MODE)
 
+static RAW_NOTIFIER_HEAD(eud_nh);
+
 struct eud_chip {
 	struct device			*dev;
 	struct usb_role_switch		*role_sw;
@@ -41,6 +46,42 @@ struct eud_chip {
 	bool				usb_attached;
 };
 
+int eud_register_notify(struct notifier_block *nb)
+{
+	return raw_notifier_chain_register(&eud_nh, nb);
+}
+EXPORT_SYMBOL_GPL(eud_register_notify);
+
+void eud_unregister_notify(struct notifier_block *nb)
+{
+	raw_notifier_chain_unregister(&eud_nh, nb);
+}
+EXPORT_SYMBOL_GPL(eud_unregister_notify);
+
+void eud_notifier_call_chain(unsigned long role_switch_state)
+{
+	raw_notifier_call_chain(&eud_nh, role_switch_state, NULL);
+}
+EXPORT_SYMBOL_GPL(eud_notifier_call_chain);
+
+static int eud_vbus_spoof_attach_detach(struct notifier_block *nb, unsigned long event,
+					void *data)
+{
+	struct device_node *eud = of_find_compatible_node(NULL, NULL, "qcom,eud");
+	struct device *eud_device = bus_find_device_by_of_node(&platform_bus_type, eud);
+	struct eud_chip  *eud_data = dev_get_drvdata(eud_device);
+
+	if (eud_data->enabled  && event != USB_ROLE_DEVICE)
+		return NOTIFY_BAD;
+	else
+		return NOTIFY_OK;
+}
+
+static struct notifier_block eud_notifier = {
+	.notifier_call = eud_vbus_spoof_attach_detach,
+	.priority = 1,
+};
+
 static int enable_eud(struct eud_chip *priv)
 {
 	writel(EUD_ENABLE, priv->base + EUD_REG_CSR_EUD_EN);
@@ -196,6 +237,10 @@ static int eud_probe(struct platform_device *pdev)
 		return dev_err_probe(chip->dev, ret,
 				"failed to add role switch release action\n");
 
+	ret = eud_register_notify(&eud_notifier);
+	if (ret)
+		return dev_err_probe(chip->dev, ret, "failed to register notifier\n");
+
 	chip->base = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(chip->base))
 		return PTR_ERR(chip->base);
@@ -226,6 +271,9 @@ static void eud_remove(struct platform_device *pdev)
 
 	device_init_wakeup(&pdev->dev, false);
 	disable_irq_wake(chip->irq);
+	eud_unregister_notify(&eud_notifier);
+
+	return 0;
 }
 
 static const struct of_device_id eud_dt_match[] = {
-- 
2.17.1