On Thu, Nov 03, 2022 at 12:57:09PM +0530, Deepak R Varma wrote:
> Hello,
> While reviewing this [1] coccicheck warning, I observed something that concerned
> me. The variable i_write_length is declared to be of u32 type. Later it is
> assigned a value DMA_MAX_COUNT * mpkt; which is 256 * u32;
>
> I am unable to estimate if mpkt (or max packet size) can attain value greater
> than 16777215 in which case the result will overflow the 32 bits of
> i_write_length. Is it safe to make i_write_length to be a u64?
>
> [1] drivers/staging/emxx_udc/emxx_udc.c:1007:28-29: WARNING opportunity for min()
>
drivers/staging/emxx_udc/emxx_udc.c
983 static int _nbu2ss_in_dma(struct nbu2ss_udc *udc, struct nbu2ss_ep *ep,
984 struct nbu2ss_req *req, u32 num, u32 length)
985 {
986 dma_addr_t p_buffer;
987 u32 mpkt; /* MaxPacketSize */
988 u32 lmpkt; /* Last Packet Data Size */
989 u32 dmacnt; /* IN Data Size */
990 u32 i_write_length;
991 u32 data;
992 int result = -EINVAL;
993 struct fc_regs __iomem *preg = udc->p_regs;
994
995 if (req->dma_flag)
996 return 1; /* DMA is forwarded */
997
998 #ifdef USE_DMA
999 if (req->req.actual == 0)
1000 _nbu2ss_dma_map_single(udc, ep, req, USB_DIR_IN);
1001 #endif
1002 req->dma_flag = true;
1003
1004 /* MAX Packet Size */
1005 mpkt = _nbu2ss_readl(&preg->EP_REGS[num].EP_PCKT_ADRS) & EPN_MPKT;
^^^^^^^^
mpkt is 0-0x7ff so 256 * 0x7ff will not be greater than UINT_MAX.
1006
1007 if ((DMA_MAX_COUNT * mpkt) < length)
1008 i_write_length = DMA_MAX_COUNT * mpkt;
1009 else
1010 i_write_length = length;
1011
1012 /*------------------------------------------------------------*/
1013 /* Number of transmission packets */
1014 if (mpkt < i_write_length) {
regards,
dan carpenter
