Thank you for providing the code and identifying the CWE-476 vulnerability. CWE-476 is related to NULL Pointer Dereference. To address this vulnerability, we need to ensure that 'partner' is not NULL before dereferencing it. Here are five possible patches:

Patch 1: Add a NULL check before dereferencing
```c
struct typec_altmode *
typec_partner_register_altmode(struct typec_partner *partner,
			       const struct typec_altmode_desc *desc)
{
	if (!partner)
		return ERR_PTR(-EINVAL);
	return typec_register_altmode(&partner->dev, desc);
}
```

Patch 2: Use a ternary operator to return NULL if partner is NULL
```c
struct typec_altmode *
typec_partner_register_altmode(struct typec_partner *partner,
			       const struct typec_altmode_desc *desc)
{
	return partner ? typec_register_altmode(&partner->dev, desc) : NULL;
}
```

Patch 3: Use assert to catch NULL pointers in debug builds
```c
#include <assert.h>

struct typec_altmode *
typec_partner_register_altmode(struct typec_partner *partner,
			       const struct typec_altmode_desc *desc)
{
	assert(partner != NULL);
	return typec_register_altmode(&partner->dev, desc);
}
```

Patch 4: Return an error code if partner is NULL
```c
struct typec_altmode *
typec_partner_register_altmode(struct typec_partner *partner,
			       const struct typec_altmode_desc *desc)
{
	if (!partner)
		return ERR_PTR(-ENODEV);
	return typec_register_altmode(&partner->dev, desc);
}
```

Patch 5: Use a goto statement to handle the error case
```c
struct typec_altmode *
typec_partner_register_altmode(struct typec_partner *partner,
			       const struct typec_altmode_desc *desc)
{
	if (!partner)
		goto error;
	return typec_register_altmode(&partner->dev, desc);

error:
	return ERR_PTR(-EINVAL);
}
```

Each of these patches adds a check to ensure that 'partner' is not NULL before dereferencing it, addressing the CWE-476 vulnerability. The choice between these patches depends on the coding style and error handling conventions used in the rest of the codebase.