### Patch 1: Input Validation
To fix the CWE-476 vulnerability, we need to validate the input to the `typec_register_altmode` function. We can add a check to ensure that the `partner` and `desc` pointers are not null before calling the function.

```c
struct typec_altmode *
typec_partner_register_altmode(struct typec_partner *partner,
                                const struct typec_altmode_desc *desc)
{
    if (!partner || !desc) {
        return ERR_PTR(-EINVAL);
    }
    return typec_register_altmode(&partner->dev, desc);
}
```

### Patch 2: Error Handling
We can also improve the error handling in the `typec_register_altmode` function. If the function returns an error, we should handle it properly instead of ignoring it.

```c
struct typec_altmode *
typec_partner_register_altmode(struct typec_partner *partner,
                                const struct typec_altmode_desc *desc)
{
    struct typec_altmode *altmode = typec_register_altmode(&partner->dev, desc);
    if (IS_ERR(altmode)) {
        dev_err(&partner->dev, "Failed to register altmode: %ld\n", PTR_ERR(altmode));
        return NULL;
    }
    return altmode;
}
```

### Patch 3: Null Pointer Check
We can add a null pointer check for the `partner` and `desc` pointers before calling the `typec_register_altmode` function.

```c
struct typec_altmode *
typec_partner_register_altmode(struct typec_partner *partner,
                                const struct typec_altmode_desc *desc)
{
    if (!partner || !desc) {
        dev_err(&partner->dev, "Invalid input: partner or desc is null\n");
        return NULL;
    }
    return typec_register_altmode(&partner->dev, desc);
}
```

### Patch 4: Pointer Validation
We can validate the `partner` and `desc` pointers to ensure they are valid and not pointing to invalid memory locations.

```c
struct typec_altmode *
typec_partner_register_altmode(struct typec_partner *partner,
                                const struct typec_altmode_desc *desc)
{
    if (!partner || !desc || !partner->dev.parent) {
        dev_err(&partner->dev, "Invalid input: partner or desc is invalid\n");
        return NULL;
    }
    return typec_register_altmode(&partner->dev, desc);
}
```

### Patch 5: Function Wrapper
We can create a wrapper function around `typec_register_altmode` to handle the error checking and validation.

```c
struct typec_altmode *
typec_partner_register_altmode(struct typec_partner *partner,
                                const struct typec_altmode_desc *desc)
{
    return typec_register_altmode_wrapper(&partner->dev, desc);
}

struct typec_altmode *
typec_register_altmode_wrapper(struct device *dev, const struct typec_altmode_desc *desc)
{
    if (!dev || !desc) {
        dev_err(dev, "Invalid input: dev or desc is null\n");
        return NULL;
    }
    struct typec_altmode *altmode = typec_register_altmode(dev, desc);
    if (IS_ERR(altmode)) {
        dev_err(dev, "Failed to register altmode: %ld\n", PTR_ERR(altmode));
        return NULL;
    }
    return altmode;
}
```

Note: These patches are just examples and may need to be modified to fit the specific requirements of your codebase.