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Message-ID: <b33fddb8-b5de-a4dc-3795-bfb3ebf44319@quicinc.com>
Date:   Thu, 13 Jul 2023 14:00:37 +0530
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Subject: Re: [PATCH V1 2/3] usb: misc: Add notifier call chain to Embedded USB
 Debug(EUD) driver
Content-Language: en-US
To:     Bhupesh Sharma <bhupesh.sharma@linaro.org>
CC:     <linux-arm-msm@vger.kernel.org>, <linux-usb@vger.kernel.org>,
        Andy Gross <agross@kernel.org>,
        Konrad Dybcio <konrad.dybcio@somainline.org>,
        "Bjorn Andersson" <andersson@kernel.org>,
        <gregkh@linuxfoundation.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>,
        "Sibi Sankar" <quic_sibis@quicinc.com>,
        Rajendra Nayak <quic_rjendra@quicinc.com>
References: <cover.1689148711.git.quic_schowdhu@quicinc.com>
 <18212c7abbb8c833cc07f8500d4905b79c49ec59.1689148711.git.quic_schowdhu@quicinc.com>
 <CAH=2Ntz8JEGp_Atsv3iToUG1WdLKvdt5GYu7a=LwgmgY7v0rvw@mail.gmail.com>
From:   Souradeep Chowdhury <quic_schowdhu@quicinc.com>
In-Reply-To: <CAH=2Ntz8JEGp_Atsv3iToUG1WdLKvdt5GYu7a=LwgmgY7v0rvw@mail.gmail.com>
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On 7/12/2023 11:52 PM, Bhupesh Sharma wrote:
> Hi Souradeep,
> 
> On Wed, 12 Jul 2023 at 13:58, Souradeep Chowdhury
> <quic_schowdhu@quicinc.com> wrote:
>>
>> 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@quicinc.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)
> 
> These indentation issues are already addressed in my EUD patches.
> Please rebase your patches on the same to reuse those
Ack

> 
>> +#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);
> 
> Probably I missed it, but you have not provided any example users of
> these APIs in the patchset or reference to another one which shows how
> these APIs are used.

Ack, the usage for this will be posted in the next version.

> 
>> +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,
> 
> Why do you need a 'priority = 1' here, it can be 0 or even lower?

Priority is 0 by default for a notifier block, since eud notifier
needs to be the first to be called in the chain to check the
role-switch status, I have kept the priority as 1 here.

> 
> Thanks,
> Bhupesh
> 
>> +};
>> +
>>   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
>>