On Thu, Mar 09, 2023 at 03:52:59PM +0200, Andy Shevchenko wrote:
> 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.
As you said, the problem is alignment.
