On Thu, Mar 09, 2023 at 02:40:10PM +0100, Oliver Neukum wrote:
> On 09.03.23 08:10, Ye Xiang wrote:
>
> > +#define LJCA_GPIO_BUF_SIZE 60
> > +struct ljca_gpio_dev {
> > + struct platform_device *pdev;
> > + struct gpio_chip gc;
> > + struct ljca_gpio_info *gpio_info;
> > + DECLARE_BITMAP(unmasked_irqs, LJCA_MAX_GPIO_NUM);
> > + DECLARE_BITMAP(enabled_irqs, LJCA_MAX_GPIO_NUM);
> > + DECLARE_BITMAP(reenable_irqs, LJCA_MAX_GPIO_NUM);
> > + u8 *connect_mode;
> > + /* mutex to protect irq bus */
> > + struct mutex irq_lock;
> > + struct work_struct work;
> > + /* lock to protect package transfer to Hardware */
> > + struct mutex trans_lock;
> > +
> > + u8 obuf[LJCA_GPIO_BUF_SIZE];
> > + u8 ibuf[LJCA_GPIO_BUF_SIZE];
>
> And here we have a violation of DMA coherency rules.
> Basically you cannot embed buffers into other data structures
> if they can be subject to DMA.
Huh?!
The problem here is alignment. But other than that I can't see the issue with
embedding into structures the instances of which will be allocated on the heap.
--
With Best Regards,
Andy Shevchenko
