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

[Souradeep Chowdhury]

On 7/12/2023 11:52 PM, Bhupesh Sharma wrote:
> Hi Souradeep,
>
> On Wed, 12 Jul 2023 at 13:58, Souradeep Chowdhury
> <quic_schowdhu@xxxxxxxxxxx> 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@xxxxxxxxxxx>
> > ---
> >   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